Hello,

currently at my uni as a project we are developing Context Toolbox for Maemo. We already have this on S60 (http://milab.imm.dtu.dk/context).

This will be a set of APIs working on different levels, starting with simple sensors readings (GPS, accelerometer, WiFi etc.), through middle layer of events managing, label storing etc. and ending with high level blocks (labels sharing via bluetooth, smart location based on power consumption etc.)

So far we have very good experience with this on S60 as students can easily create a context-aware application, some of them being exactly what you are describing here.
We should be ready with first (still rather basic) functionalities in mid-December. The toolbox is written in C++ and it nicely hides all the sensors management stuff.

At this moment we do not plan API for profiles on Maemo, simply because some things are in focus first. But it should be possible to be done. With this API, writing the application mentioned would be extremely easy.