Hello everyone,
The theme of this thread/question resembles that of one here:
http://talk.maemo.org/showthread.php?t=31331
But, that thread is more about call forwarding, not direct usage of available WifI to receive and place calls with Nokia n900.

Here is what I am looking for:
Is there an application or a setup way to automatically (or manually) switch the phone for a wifi use to receive and place regular cell phone calls?
This is NOT about call forwarding services, this is NOT skype calls or anything in line with that.

We had blackberry using t-mobile in the household in the past, which did just that, per corresponding phone's settings - whenever wifi is available, the phone would switch to use it for regular calls. I therefore assume something like that should be technologically possible, IF n900 has what it takes, hardware wise.

I have read that possibly t-mobile may not allow for this to happen, but once again, I know for a fact that this works WITH t-mobile, but on blackberry device.
I guess it is possible that t-mobile "lets this feature to work" on blackberry phones sold by them only, but then I don't see why can't I just go to my t-mobile account and specify my phone as if it was blackberry. They don't have n900 listed anyway and as of right now I don't have any phone model specified on my t-mobile account...

Any thoughts on this?

Thank you in advance and I do think that the feature like this should be of enormous usability in households with some "blind spots" for their mobile coverage.