My experience with a VGate OBD2 Bluetooth dongle...
Got this today and ran out to play. I connected it up to my 1999 Suburban first and had no luck. I then hooked it up to my 2013 Malibu and it worked perfectly with AutogaugeX and CaDash. Both vehicles are OBD2 compliant. The only difference between the two is the Malibu uses CAN and the Suburban uses VPW protocols.
After figuring this out I tried the following apps on the Suburban:
AutoGaugeX connects to the dongle fine. Status at the top says "Connected to car" but no data is transmitted to the app. RPM stays at 0.
CarDash connects to the dongle then disconnects after a few seconds.
Motorist showed no data but couldn't tell if it stayed connected to the dongle.
ODB Info San was the only one that showed any information at all and that was voltage but looked like the free trial version times out before any other info come through. This is the only app I found that let me select what ODB protocol to use.
I tried the Use Freely ELM 327 app but no luck keeping CarDash connected.
UPDATE Edit:
Had an idea so I hooked it back up to the Malibu and using OBD Info-San played with the protocol settings. If I didn't set the correct protocol the app either wouldn't connect at all or I would only get voltage and nothing else. When using the Auto Negotiate setting it was hit and miss if I would see any information. But selecting the correct protocol always worked perfectly. I was also wrong about the free trial timing out so I need to play with the protocols on the Suburban and see if I can find one that works.
My suspicion is that while they say these are OBD2 compliant, they have a problem negotiating older protocols. People having problems, what protocols do your vehicles use? You may be able to tell by looking at what pins are populated in the connector. This web page is what I used to find mine:
OBD II Connector Pinout
I will try again tomorrow on a 2000 Cougar and see what happens with it. It should be using the PWM protocol.