This started because I wanted to monitor my transmission temps on the 5spd A750 auto (there's actually two temp sensors in it).
Bought an OBD2 wireless dongle, and grabbed the iOS app called OBD Fusion ($15) to run on my dash mounted ipad mini 3g (which i use for offroad navigation and satellite imagery on big trips) ... which offers all the standard PID's for generic OBD, but also has additional model specific connection setup for each actual engine which opens up hundreds and hundreds of extra things, and connects into the "network A" bus of OBD, rather than the generic.
Only trouble was it didn't have the 3.0 or 4.0 listed for Hilux, but the guy who makes it is aware and is sorting that out (you'll see in my screenshots that 4 of the metrics are zero ... those four shuld light up once the developer releass next update).
The app did have the 4.0 engine listed, but for the FJ ... and it has a different ECU to the Hilux , so it still wouldn't connect.
Anyway, here's a couple of screenshots and a video of it in action, I think its pretty cool (the wife just thinks I'm a nerd, but hey she had every chance to run).
There are literally hundreds of different metrics you can analyse, chart.
There's few things I need to clean up, and some metrics give odd results (throttle position is a hard one, but I'm still using generic OBD2 ... waiting on the Network A access and should get some better access).
Cruising (someone else driving)
Giving it some stick (someone else driving).