My background is in surveillance products (the engineering, design there of) and such is not in production for a few reasons. Mostly due to costs.
However this is not to say we can't use any old Android cell phone to craft the solution. I did write the app for this on Windows Mobile years ago and today would port it if the money was there.
-> But there's a big issue with BlueTooth and that's the range. As a surveillance product this would fail big time due to the 30 foot (tops) range. I'm sure you have a niche application so I'm part with you can do this. Just write the code.