Got my dongle today. Plugged in fine and worked first time with my Nexus 5 using Torque.
Mucking around with dashboards and stuff. Obviously not great when driving as you don't want to be eyeballing a phone, but reads codes and stuff. Seems to be a reasonable amount of development put into the app too.
You can set the gauges to record highest values etc, so in a race car you can check afterwards. Also the gauges can flash when over a certain value. Don't seem to have any audio/alarms though which would be alright, but there is a tiny bit of data lag from the
ECU to the phone.
Ideally you'd have it running on a tablet in the dash somewhere if you were serious to use the gauges and not just the CEL checker.
Worth the app + dongle purchase though for some self diagnostics.