What surveillance? This is people voluntarily reaching out.

I totally understand aleksandyr. I can't wait to see what you will come out with!

This is exactly the kind of applications that would make use of my idea for the application, I already have the N800 and got it with the discount code for two ideas I was not able to release (too much work in the office :/), but I was going to try, one never knows.
My idea is to extend the gpsd daemon into the tablet (dunno if there's this service already, going to study a bit about it) by implementing a bunch of integrated services:

1) Location based events
The idea is to have a database of locations (user POIs) and to send custom DBUS messages depending on: being at, moving from, going forward a location.

2) stream of positions (what currently GPSd does, but "broadcasting it" locally.
One streaming endpoint, multiple receiving endpoints.

3) same as two, but broadcasting the stream *outside* the tablet, over the Internet to your authorized (and willing to receive it) friends.

On this service one can implement several interesting applications:

a) alarms based on location (warn me if I am near a place I'm interested in: post office, bank, ATM whatever)

b) logging (you have been near: this, this and this (based on your interests you've specified)

c) tourist mode: I'm in Rome and I am walking around the town centre, I don't want to go look at a map to see what's around me *everytime* I move. I want it to KNOW what I like and WARN me when I am at a walking distance from a store I might like. This is similar, or probably the same, as point a). Example: The tablet knows I like to drink coffee and I'm following my Italian friend to a place he thinks I like. While walking, in the neighborhood there's a coffee shop I would have never noticed. The tablet warns me about that and I might choose to let it drive me there.

d) I'm in Rome near the Colosseum, give me infos about it. Download the podguide of the Colosseum, video, audioguide.. whatever service I'm registered at.

e) nearby friends: I am walking down Fifth Ave in NY, my friend's walking next block. Warn me (warn him). Ok.. "let's go drink a coffee".
(the topic of this thread, is it?)

f) keep always updated with nearby free hotspots (FON, and the alike). When I look at the tablet, I want to know that 1 mile away there's a free hotspot.. ok, let's go there and look if I've got the e-mail I was waiting for.

g) you name it.

I want it a service, like the "presence" service, of the tablet, not as a standalone application I have to remember to start up before leaving.
I just want an option in the control panel (similar to the WLAN autoconnection) like "check every 5 mins if I'm walking outside the house and then activate the <whatever> mode".

I just wrote it down, I'll clean it to make it more readable, to look for overlapping features with GeoClue, MaemoPlazer etc.. it might be the framework they could base their service on...
Anyway, this is just the basic idea.

But what do you guys think of it ?

I'm not sure I agree with some of your other suggested uses, some of them seem to be suggesting that technology should dictate our choices rather than enjoying our surroundings through idle discovery, but that's just me and that isn't to say they don't have merit.

What did pique my interest is the above statement as it made me realise that the tablets, through GPS, can now determine (or at least guess at) the owners activity - by sampling the current location at regular intervals, the Tablet can make an assumption about the users current activity, ie. stationary, walking (speed < 10km/hour) or in/on some form of transport (car/bike/train etc.) when speed exceeds say 30km/hour (although when driving in London the Tablet could think you are stationary or at best, walking). I wonder if this additional information would be useful to a location aware application?

Well my application will be *just* for the framework.
On top of hit many applications could be built, those are just examples and their policies will be their problem.

It will. Application could process the updates and react accordingly.

I suppose the current activity (driving or walking) could be a factor when suggesting possible places of interest - I might be interested in a coffee shop or post office when out for a stroll (though I'd probably have plotted a direct route to the nearest post office if I was in need of their services so maybe not a good example ) but less interested when bombing along in my car.

That's exactly what I meant with "accordingly". The framework will "bomb" (or may be not, we'll see) with updates. The application that will receive this bombing has to filter it "accordingly" with other variables (like the speed, the time and so on)..

But likely, you got the main idea, so my writing was not so totally bad

The Geoclue developers have thought a lot about this, and plan to allow you to specify to each application what level of detail you want to provide - so, for example a mapping app like Maemo Mapper will want the best accuracy possible, but you may limit your Jaiku / Plazes apps to only be given the town name, no greater accuracy. This should be user definable, allowing *you* to choose what level of detail each app / service gets.
Geoclue, and many other location based services solutions are mainly about providing your location to search engines to allow it to tailor the content to you (as opposed to providing a full-on tracking service). Yes, you can use the likes of Geoclue with a tracking service, but that's your choice, it's certainly not forced upon you. Geoclue can still help here though; I could hopefully use Geoclue to limit my location information to something like "Home", so I can happily publish to all my work colleagues (or even the whole Internet) that I am "Working from Home" without letting any of them know where "Home" is, whereas I may want Google to be given a more meaningful location to allow it to provide information on services close to my current location.

I, for example, upload pictures to Flickr with location information of where they were taken, but then limit access to that location data to friends and family only (as a default). Most LBS (location based services) work like this, and those that don't will (in my opinion) never be truely popular due to privacy concerns.

anidel - it would seem to me that's it's possible what are you suggesting is the middle layer between Geoclue and stuff like Google Maps - in essence a logic engine that takes the outputs from Geoclue and feeds it into apps like Maemo Plazer / Maemo Mapper / other applications as and when appropriate. If nothing else, I would recommend you join the Geoclue mailing list (if you are not already on it), and discuss your ideas with the people on there as well to see how best it fits into their architecture.

Either way, it sounds very interesting, and hope something comes of this discussion...

Just in case anyone was wondering, Maemo Plazer is currently broken thanks to API changes made by Plazes in the last few weeks.

There's a version of Maemo Plazer that you can download into the SDK_X86 emulator which has been broken for months

Let's hope this gets fixed when they fix the main tablet version...