For the type of applications I imagine, I wouldn't need more than 1mA of current...just enough to run an attiny-like microcontroller and blink a LED on occasion before going back to lowpower mode. It seems NiMH just doesn't come in those small sizes. I don't know much about ML, I'll have to look into if ML and LiR in the smallest coin size are safe enough. Actually now that I've thought about it more I might be able to just use a small supercapacitor for around an hour if I'm really careful with energy consumption.