Between 9AM-5PM today, CABiT (a taxi booking app) will offer free rides to anyone who travels in one of their 22 green taxis.
So looking at the app, all of the cabs displayed are green so basically book a fare and it will be free. Given there are 22 and this has been advertised, there may be issues with availability. Screenshot of app. I see taxis as far north as Mill Park and as far south as Moorabbin, so a pretty big coverage area.
Alternatively, there is GoCatch which you should be able to score a $25 credit or Uber with a $30 credit. However, those are for new customers only so if you have signed up for those, then CABiT might provide a good option for a free taxi today.
iOS App
Android
Website - Book via website for non-app users.
132222 - Book via phone.
I'll give it a go. Hopefully the driver will be happy to leave the meter running while I pick something up.