Yep, Yo bikes. There are 600 of them in Bristol, so I'm told. Certainly lots on Gloucester Rd and around the Centre. Cost £1 an hour up to £5 a day, but I've no idea what their definition of day is. They have a 3-speed hub, dynamo lighting, little rack at the front, inbuilt horseshoe lock so you can leave them anywhere. You have to download an app to hire them. I don't know anyone who's ridden one yet.