I see that the Gen3 devices have bluetooth. Has anyone used one to communicate with a bluetooth ODB2 reader?
Welcome to Particle Community.
The BLE support has only just been released in 1.3.0-alpha1 - you can download it from github but the webIDE or workbench are not supported yet as it has been released to a limited group to try out. In the next few days or weeks you should be seeing a load of example projects as well as 1.3.0-rc.1 available.