Gopro has a remote control. However the GoPro wifi system is known to cause interference with the flight control system of the Phantom 2. My Gopro 3+ Black can take stills and video at the same time or stills can be set up in increments of seconds in time. I'm not sure what the Silver edition is capable of.
You can set the go pro to take still pictures at intervals while filming video. It does not allow you to snap one exactly when you want, but if you set it to capture a still every 5 seconds that should get you what you are looking for.