So... u-SD cards do work better with just one partition, and if you want to put anything but single DOS partition on u-SD card, avoid Kingston cards. Sandisks seem to work.
TI Chronos may be cool... but it seems like it is 30 years old technology. See historical Seiko watches. And yes, alphanumeric display would be useful.
And yes, that means that I do have some ideas what to do with TI chronos to make it more usable. In mychronos project, emulator is implemented (now with SDL output, thanks to metan), and I'm playing with user interface.
Major UI problem on Chronos is that the two lines of display are controlled separately. So... you can select that you want to display height and "SYNC" message. Or variometer and temperature. (But variometer will not work in this case). In mychronos firmware, I make it behave like traditional watch: just one mode. Where there would be unused line on display, I display time... it is watch after all. Now, I'll just have to fix all the glitches, and probably merge it with OpenChronos project. [Perhaps someone willing to help is reading this? Testers and "yes that would be nice" messages would be helpful ;-).]
Another idea I'd like to explore is automatic connections to the computer. Like... TI Chronos is watch, but it does not keep time too accurate. Once-a-day synchronization with computer (which hopefully synchronizes via NTP) would make it very accurate again... also opening possibilities such as your appointments on your watch.