oBike, a dockless bicycle sharing and Yarra river anchor system, is offering unlimited free rides this weekend. For existing users, just scan and use as normal. New users need to put a $79 refundable deposit (or $10 for students).
I've used this overseas so once you have an account you will be able to use it worldwide. I used it in Amsterdam and the bikes were identical.
As for the bikes, they are awful as they are single speed, heavy and have no puncture tires with thick treads. However for relatively short trips they are OK. I was going to use it today anyway as I need to take a one way trip so even better it's free.
Most of the bikes have helmets attached to the lock.
Yeah they aren't in Brisbane or Gold Coast.. :/ They only operate in Sydney, Melbourne and Adelaide.