One thing I think I have noticed, it looks like the SMS that I send needs to be the exact password and not even have a space after it. For example if my password is "hello" and I send "hello " then it does not activate the reporting. Also can you confirm that password is case sensitive?

Case sensitivity is a bit of a pain - imagine the situation - I have lost my phone and I send my password "hello" from a friends phone, but I don't know how to use his phone properly and I don't realise that it automatically puts the first character as upper case. I end up sending "Hello" and the app does not report back. This could waste valuable time.

Another suggestion - what about if the app looks for the key phrase or word in a whole snetence. So if my password is "hildon" i send a message saying "Please phone aunty Hildon" and it activates reporting!