Hey, I'm only 39, I'll worry about a medical dogtag when the time comes!
Seriously, for me this is more about tracking my own health and learning about my responses to things over time. This is also as much about 'fitness' as 'health'. (Of course I realize thats an artificial distinction, but the market for these software products certainly views them distinctly.)
Anyway, the more I think about it the more I figure I'd better DIY this in Excel. I'd hate to have lots of data in some application and have the vendor go bust. Better to organize it myself in Excel with proper backups.