Thanks for the feedback. I must say I currently have no idea how to implement such mechanism and not sure if it would really make things any safer / private. Any pointers to examples / concrete suggestions for implementation are welcome

Using some sort of public/private key signature is the best protection I can currently think of, but I think even that would be hackable and perhaps not worth the effort. In the end, without some sort of platform support for sandboxing apps / protecting IPC, it comes down to trusting all the software you have installed on the device not to be malicious.

Br,
Heikki