I'm considering putting a small lithium battery on my Super OSD Pro boards. The battery would provide power to the RTC. I am wondering how small can you get a battery? I don't really care about capacity, I expect current draw to be less than 1µA, so it's really only size I'm looking for.
Best solution would be one that is removable, because I'd like people to be able to replace the battery when it does go flat.
And I'm open to suggestions on how to control the power to the main bus which has some heavier current draw devices which would overwhelm the 1µA for the RTC (the RTC is provided by a PIC24F in deep sleep mode.) I'm thinking of a power monitor, but it needs to be able to switch at least 100mA for the MCU when it's running full speed.