Yes, it would be nice to have such a thing that integrated easily into XOOPS, but you can always install a second application next to XOOPS and link to it.
I've done this successfully with phpCoin and phpAdsNew, both available throughhttp://www.sourceforge.net
This leads me to the main point. Go tohttp://www.sourceforge.net and search for a dating module that uses MySQL and preferably PHP (Though there's no reason why it has to be written in PHP).
Here are a few I've seen that are in PHP:
absolutemeeting.com match/dating engine
phpDD
phpMatchmaker
Hope this helps.