Forensic-self-check on my phone using my phone?

Hi All!

I may run in to the following problem.

Problem description
I sometimes have to leave my phone over to 'others' when I visit different locations. When I leave the location I get get my phone back. However, during the time the phone is not in my posession and the phone may have been tampered with. (The tampering that worries me is having eavesdropping software installed or software with similar means…)

Since I might be on the road when this happens I need to make sure the phone hasn't been tampered with (software-wise) and I do not have a computer with me at the time. Any ideas on how to do a "forensic self check" on the phone to make sure that the phone is what it was before I left it at the 'door'? (not tampered with)

An idea I had was to implement a hash-calculating function using java and install it on the phone, Nokia N79 (or a different version for Iphone)(calculate it before I leave it in and make the same calculation when I get it back and compare the two) But I am not sure that it will work since the hash may return a different value even though it hasn't been tampered with.

Thanks in advance!

// profiler