These bikes randomly started appearing at Prince Alfred Park in the city one day and it turns out they were from two separate bike hire startups. The bikes can be hired through an app which tracks the location of each bike. The great thing is that bikes don't have to be returned to a bike docker, they can just be left where they are (in a reasonable location where bikes can be parked). More and more of them have started appearing, usually around the public pool area.
A few have started popping up in my own suburb. Sydney with its busy and not-so-flat roads is not the most bike friendly place but it's a great idea to get more people cycling. Not having to dock it is particularly useful. I tried out the bikes in London and sometimes I'd reach a docking station with a few minutes to spare only to find the docking station full! The options were then to cycle to another station or wait and hope someone came to rent a bike. Even with a docking station app you'd sometimes end up cycling a bit further just to find a place to dock.
Should be interesting to see how it goes as overseas experience has shown bikes being stuck up trees and dumped on the street. Admittedly not sure if those bikes were left there for real or for instagram stardom.