And at least 3 people who have use the A5-V11 (with battery) hardware, and Fusee-Lede. Seriously, the battery version of the A5V11 is about the size of a candy bar. It fits neatly just about anywhere, and doubles as a convenient additional battery for road trips. They are also super cheap.
As for what is inside the TX dongle:
There were some posted renderings. It contains two large electrolytic capacitors, a charging circuit, a USB high speed switch, and a low-power micro controller.
There are a number of projects already being created that are either internal modchips that do the same thing, or are tiny microcontroller based injectors. (Like Ninoh-FOX's build.)