This app was mentioned in 2 comments, with an average of 1.00 upvote
Don't line up at the machine, use Pay24 iOS / Android.
Now that PTV does most topups in less than an hour there's not much reason to use the machine anymore.
There is an app called Pay24 for iOS and Android - it's not an official myki app but it does sent you notifications when your balance is low, and stores credit card details for two-tap topups.