I agree with you there that actual wire transfers would probably not be the best way to go, but Western Union does offer other forms of accepting online payments.
http://www.westernunion.com/info/bsC...asp?country=U1
Possible things of interest on there:
Western Union® Auction Payments (send/receive online payments - U.S. + "several other countries")
Western Union® MoneyZap (send/receive online payments - U.S.)
Western Union® Phone Pay® (take check payments over the phone - U.S.)
Western Union® Quick Collect® (receive payments online or from Agent locations within the U.S.)
Western Union® Quick Pay (receive payments from Agent locations outside the U.S.)