I have two legs, but one of them is only 70% power due to a broken femur injury when I fell from my BikeE on some wet leaves.
I added an electric power assist to the BikeE and I'm having a great time again.
I'm sure a trike is in my future, as I age, and balance starts to become a safety issue. Check out this website for the latest in recumbent power options:
http://www.ecospeed.net/index.html