What to do with a bunch of slightly depleted 9V batteries?

[Dave Britten]

For the next few months, I have to give myself a 12-hour IV every night (nutrition via IV, basically; look up "TPN" if you're curious about the details). The IV pump I was given runs on a single 9V battery. I am instructed to use a fresh battery every night, and am provided with them accordingly.

It looks like the batteries have about 8V left on them once the run has finished in the morning. Rather than chuck out ~120 batteries with useful life in them, I'd like to find something interesting to use them in. Calculators, computers, portable video games, whatever. Off the top of my head, I've got a couple things that run on a 9V:

TI-30
Sinclair Cambridge Programmable
Psion Organiser II (a few of 'em)
Milton Bradley Microvision (pretty sure this uses a 9V)

What else should I go hunting for on ebay, knowing that I'll pretty much never have to buy any batteries for it out-of-pocket?