Expected growth in the wheelchair market. A growing percentage is expected to be seen in the sport wheelchair market in which Rowheels products situates itself: 

https://www.coherentmarketinsights.com/press-release/wheelchair-market-to-surpass-us-151974-million-threshold-by-2025-globally-with-north-america-positioned-as-growth-engine-326

Differential planetary gear system for producing complementary levels or forward/reverse drive: 

http://www.freepatentsonline.com/4497220.pdf

 
Device to reverse direction of a unidirectional powered drive: 

https://www.google.com/patents/US8777795