One typical design places the heavy NiMH pack in a location where it reduces the chairs stability and is right in harms way, should the chair fall over. Also the battery state indicator often is part of the battery pack:
This tech is old, cumbersome and in some areas just poorly designed. To make the world a better place I want to design adaptors that can be fabbed in a typical hackerspace, or even at home. The adaptor will then be hooked up to a microcontroller board that fools the chair into accepting the new battery as its own. This not just allows the pack to be placed in a better location but the user can determine the desired capacity. So a person that mostly rolls around at home no longer has to lug around the battery for a moderate commute.
The microcontroller board is intended to be one oft the usual suspects and can very well be equipped with some flavor of radio to make the battery state information easily accessible to the user.
Once the battery is talking to the phone, it can be made to talk to its nav software as well, so the battery can inform its owner when it is time to turn around or consider public transportation for the way home.
Another way to combat range anxiety would be the option to integrate a charger so one can top up the battery when visiting friends or public places.
I want to make the design to mostly consist of standard components to make it really accessible and easily built, ideally by end users with little to no experience in building electronics.