I logged to my Mint (mint.com) acct to see if by any chance they had an option for the NW Visa Buxx to be added there, they didn't. They did have one for the US Bank Buxx though.
After I searched for NW (searched for "visa buxx" to see what showed), I went ahead and clicked on the link that tells you to request a bank to be added to their site, it asks for the following fields, (putting them here for copy & paste purposes):
Name - Nationwide Visa Buxx
Home page:
https://www.visaprepaidprocessing.co...ages/Home.aspx
Login page:
https://www.visaprepaidprocessing.co...es/SignIn.aspx
Maybe if a bunch of us ask Mint, they will be more inclined to add this, so please consider submitting a request after you've logged to your Mint acct. Thanks.