I bought a wi-fi OBD-ii that connects to my iPhone a few years back. Works great on most everything except my '96 SL. It takes forever to synch, gives weird codes that change if you start, stop, and restart the car, and sometimes it cleared the codes but sometimes didn't. So, if you get those responses, you're not alone.
And all that said, I suppose I'll try to hook it to my aunt's '97 this weekend just to see if it behaves differently.