This isn't exactly what one might term the perfect solution to the problem, but there seem to be a few people coming out with enterprise Mobile Device Management solutions. Here's a few I found (I'm still not sure if our customer'd want to go for these, but the existing approach of chasing everybody up per email just doesn't scale!).
Trellia
MobileIron: Almost impossible to get any useful non-corp-speak info from this website.
AirWatch: The only people who seem to have bothered to actually tell you how much it costs ($3/device/month; pricey!)
