I saw an ad the other day for a product so simple yet so ingenious that it had already been invented: automatic sliding doors. The unique thing in this case was the fact that it was packaged as an add-on motor and sensor for existing domestic doors. Genius! Makes me wonder why nobody else ever thought of doing that.
Mokalus of Borg
PS - Perhaps they did, but never had the cash to get it off the ground.
PPS - Or the determination, or the right connections...