The initial momentum for the till system came from not being able to find suitable solutions out there to suit our needs. To that end, here are is an incomplete list of things I need a till system to do:
As 1,2 and 3 would be in my hands, I thought I should investigate #4. As Google Docs use keyboard shortcuts, I was fairly certain this was achievable.
After an hour or so, I was able to come up with a solution with a mac hack for command rather than control.
You can download the version I am using (with the mac hack already in place) right here.