Wanted to post some pics of my 3DR radio with Bluetooth. I am very pleased with the outcome.
I started off with a pair of Ebay 3DR radios, burned those up the first night of testing, and ordered another set. Ultimately learning a lot along the way. What I have assembled is a 3DR ground radio, a HC-05 Bluetooth module, a constant voltage power supply, a power pack from recycled cell phone batteries and a voltage meter all nestled in an old plastic playing card case.
Starting with the battery, it is two Li-ion cellphone batteries in series. I even took the time to add a balancing plug, scavenged from another worn out pack, and what I have is a 2S 1300mah battery. I will say, the internal protection circuits seem to mess with the charger somewhat and the charge rate drops off fairly quickly, but it should last all day. Next I added a constant voltage power supply that will accept up to 30 volts, adjusted to output 5 volts. With this I should be able to use any 2 cell or better battery that I have laying around to power to everything. On the input I added a voltage meter to monitor my overall charge level. On the output is an led so that I know the CV power supply is working. Then the Bluetooth module is wire directly to the power supply, with a 3mm LED on it status pin, so that I know when I have an active connection to the BT module. Lastly the radio is connected with a plug to the pins on the BT module so that I can still unplug the radio and use it in a computer via USB if needed.
Connecting the the data wires to the radio was tricky since the radios I used are on integrated board with the serial converter. But after doing some inspection I was able to find a decent tap point. The radio with a breakout board should be much easier.
Word of advice, if you attempt to tap the circuit board like I did, make sure you securely attach the wires to the board. If you don't, manipulating the wires can rip the copper traces clean off the circuit board. Ask me how I know!
The only thing left is to get Mission planner to open my BT COM port. The 3DR radio program works great, and my tablet works great.