That's pretty cool in general, but there are a lot of android users, and who knows when that will be available for them

To show clients that you've been tested?  Or you'll only see people who have a recent std test and use the app?  Because if there were still people looking to make an appointment despite your other restrictions, this will probably reduce it to zero..

might just have a small problem if that app was discovered on their phone. Just sayin'.

Like the first overhot McDonald's coffee ever spilled.

First of all, most guys would never agree to this for screening. Hell, some won't even provide their real name. Doubtful they're gonna be sharing STI test results with you (which, undoubtedly will include real person info).

That aside, you have no idea how many sexual partners your client may have had between the time of testing, and the time the results are available to be transferred to you, via this app.  

What this app does is really no different than someone bringing a paper copy of their last test results to a session with you. In a real world relationship this might work. But it's meaningless in the context of P4P.

There are so many ways this could go wrong if you place trust in this for your own safety