@inzimam and @msa, at the moment the app is under construction, the code posted here was rather a POC. It's taking a while, but you know how it is, with Christmas and all.

@bongo, I have written a daemon that sends dbus signals on state change. It is optimized a bit, so it should be good enough to sit there as a standard daemon.

You can access it from

values are 'open' and 'closed'.
Polling is done every 10ms, footprint is acceptable.
I haven't found any smarter way than actual polling from the file, as inotify read() doesn't work with pseudo-file system.
There is a bug opened for handling of proximity sensor in Maemo.