Please visit their website scantool.net/obdlink-mx and find the options. I have been using the obdlink mx for quite some time. It works flawlessly. It supports almost all of the soft wares that are available in the market. Most of the Chinese devices do not work.
Bidirectional capability for Car Gauge Pro is spotty at best. However, I have been able to toggle my secondary air pump on/off on my 2001 Blazer and my EVAP Purge Valve on my 2004 Avalanche using Car Gauge Pro and a BAFX Bluetooth OBD2 adapter (as sold on Amazon). So I can say that the bidirectional control is possible through Elm and Bluetooth.