What OBD II device is best for use with Watchdog?

I dare say that this is a question that has been asked many times before so excuse me for doing so. I have recently got my first PHEV and want to use watchdog with it. I have an OBD II which works but loses connection easily. I have a Kindle Fire 7 which I have accessed the play store on as the device to connect with and also use it for the PHEV II app, which works fine.
I think I need a better OBD II device and wonder what the favourite choice is for the Outlander. I do not want a wifi version and I am not sure watchdog will work with that, instead requiring Bluetooth.
Any comments welcomed!

I started with iCarSoft i620 (I think) but had to remove and replace it to get the thing started each time
Now using Vgate iCar Pro BLE 4.0 and that's working fine.
Both were around £40. You can buy much cheaper ones, but they may not work very well if at all.

I have just got this working using a vGate iCar 4 BLE which I got for £27 on Amazon. It seemed to need a "kick" to get it working properly by running an OBD test on it but since then has been fine.