I miss the old CashKeys[1]. Some cities had a digital 'key' (basically an EEPROM in a funky key-like TRRS form factor) that you could buy and preload $10-20 at a time on. When you clicked them all the way into the meter, it acted like you inserted one quarter. You'd pull it out a click and click it back in, and it'd drop another 'quarter' in. Repeat as much as you needed, and you could mix the CashKey with actual coins being dropped in the slot.

They lasted to the mid-2010s, when Duncan stopped selling keys and software and eventually, support.

[1] https://thumbs.worthpoint.com/zoom/images1/1/0816/08/duncan-...

https://ggwash.org/view/35377/its-a-little-harder-to-pay-for...