I have been using Hybrid Assistant for almost a year now and I an thoroughly impressed! Not only can I see active details like instant MPG but I can see fuel levels!
The one thing I need you to know, you should not purchase a cheap OBD2 Bluetooth device!
I learned the hard way and tested close to 10 different OBD2 devices and they all lacked the needed technology to properly monitor my Prius Plug-in Hyrbrid.