Interesting idea. I already have my phone propped at the top of my keyboard. Biggest advantage of the STRIKE 5 is the OLED display section, makes a great rest for my phone. Adding in the communication between phone and keyboard is a very niche feature. Definitely overprice also!
I've been using Roccat's Power-Grid on a cheap 7" tablet for Elite Dangerous and I can see where they're coming from with this.
I love the idea of being able to hold the tablet in place on the keyboard and power it as it goes. I think the switching between the two devices button is a good idea if you're not in the middle of a game. Well maybe it would work with slower paced games as well. It would be nice to be able to type on the tablet without having to pick it up.
I find I'm often switching over from my main display screens to my ancillary panel and it's reasonably quick as long as you're not in the middle of combat. I usually have a web browser or iTunes open so if you didn't have multiple monitors then yeah this tablet/phone stand would work well.
I don't think anyone would really answer their phone half way through a round of counterstrike or whatever.
Ultimately though it saves a little bit of desk space and the price of either an extra Bluetooth keyboard or a tablet cover with built in keyboard attached.
Probably not worth the price premium but I agree it's an innovative idea.