you can always try the torque application in the market, although you'll need a bluetooth OBDII adapter. I have one of these on the way to work with torque:
PLX Kiwi Bluetooth - Connect your Droid mobile device to your car's OBD2 OBDII Port.
Ian Hawkins
http://market.android.com/details?id=org.prowl.torque
I bought one of these readers back in May. You definitely get what you pay for. I got one for about $30 and I can get the codes and a few items, but had problems using the app and setting up the interface. I ended up taking my truck to a friend that had the $1k unit to figure out the problem.
Not sure but I think the system will only send data at certain times. I had to do mine while it was in park.