Yes, your link to Amazon is the type of Qi charger that I have in mind. I did find other Qi transmitters (like this http://afdpower.en.alibaba.com/product/913029476-218781306/Qi_Compatible_wireless_charging_transmitter_module_9V_solution.html) that are capable of dealing with 9v or 12v, so voltage shouldn't be an issue. It would be good to hear from people who have done this in order to make this easier.
The DIY method you mentioned is actually not that trivial, since I will have to build a somewhat elaborate docking station that supplies the right power and with the contact points in the right place, and the docking navigation will also be harder than using wireless charging. I looked into the wireless charging thing mainly because it appears to be simpler, because the docking station will be just a Qi transmitter, and navigation will involve only moving to a marker on the floor with wide tolerance.
Without auto-recharge capability for this autonomous GoPiGo, it would be a real chore having to constantly replace its batteries all the time.