The Spinido DJI Battery dock for Phantom 2 and 3 looks like it could be a great accessory for Phantom owners. Compatibility with both the P2 and P3 is bizarre, though, since the connectors are different. This could be a great alternative to DJI’s 4-battery Charging Hub. Both this battery dock and the DJI one charge only one battery at a time, but at least that all charge up without you having to swap them out.
Note that I haven’t tried the Spinido dock personally—let me know how it works, if you buy one! (initial Amazon reviews are good)