The last time we played Dungeons and Dragons, we were in a situation where we were tracking the duration of a Bless spell, a sleep spell, how long a torch burns for, and maybe a couple of other things. We were talking about coming up with an easy system for tracking the various spell durations, conditions, and fuel expenditures when I hit upon the idea to get an abacus!
Every abacus that I have seen has at least ten “beads” per row, which is perfect for tracking effects that last for a minute on a round-by-round basis, and really for anything else you need to track. Even better, the ones that are made for kids always have different colored beads on each row and generally have at least five or six rows, and it looks like they retail for about 15-20 bucks. That’s pretty cheap for an elegant solution to duration tracking that everyone at the table can see and quickly understand. I’m even thinking about crafting some Frankenstein’s monster involving an abacus and a whiteboard to make it even more clear what is being tracked by what with this system.