Any one try this this thing out? wondering if it works i have my doubts.
http://www.primediscs.com/proddetail.asp?prod=flyingtach (http://www.primediscs.com/proddetail.asp?prod=flyingtach)
that picture makes it look like it's sitting on top of an ultimate disc. might not be exactly what you're looking for.
You can buy 'em off Ebay and put 'em on whatever disc you want.
http://cgi.ebay.com/Tachometer-and-Flight-Timer-Module-for-your-Frisbee_W0QQitemZ170384073171QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item27abaea1d3