Editor, the DJI Go4 app records sound to the 720/1080 proxy on the tablet, so it can be done - they added the facility recently and it caused a few numpties to be concerned that DJI would hear everything back in China
julie-Dog, If you're using something like the iPad, then you want a TRRS mic like the Røde SmartLav+. Or you can get a TRRS to TRS convertor to use a normal small mic/Lav, or something like the Røde VideoMicro or VideoMic. You can then export and sync the tablet footage with the higher res aircraft footage in post - they should (theoretically both be the same length)... probably be better to use the lower standard frame rates though as you might get some drift in sync if you use 50/60 or 120 fps.
If you're using Android tablets, then you'd need to check what sort of input they have - if the headphones have 3 silver bands, then it's TRS, if they have 4 silver bands, it's TRRS.
oh, and in most cases plugging a mic in will disable the sound output, so beware you won't hear any of the dji verbal warnings i.e. for recording home point etc.
Lav's would be good if you just want to get your voice as you can stick it on yourself and it won't care which way you face as you fly. VideoMic etc are more directional and you'd probably move in/out of best sound position.