Details are on WorldBridge site under Additional Services. It's settlement priority service he wants.
Briefly the procedure is, after making online application and getting biometrics done, his wife should go to WorldBridge site and pay $300 for priority service. She should then print out the receipt, put it on TOP of her supporting documents, and write in large letters 'Settlement Priority Service' on the outside of the package and send it off to NY consulate on the same day. This then clearly identifies the package as priority, will be extracted from other packages and put on the top for immediate attention by UKBA. With a bit of luck she should hear from them within 48 hours of the package arriving in NY. Documents with visa will then be sent back by overnight delivery. I think she can only mail the package, not hand-deliver it to the consulate.
Make sure she gets a New York City certified marriage license, and to speed it up, she should hand deliver the signed license to the vital records office. This should get her the needed certificate (plus a few extras which will come in handy) within 2-3 days. This is the normal procedure but she should check locally in case it's different.