I know this is off topic a tad but as a guest I dread those Zenbu hotspots. Why not go with Ubiquiti gear and use their built in hotspot + voucher management service (if voucher management is a must).

Edit: Also both Cambium and Grandstream wireless access point gear has the same sort of hotspot management however have not used this feature. Grandstream is an all in one device (access point + wireless controller) that could be a go.

skyplonk: Never thought about Grandstream. I have a GWN7000 and some APs up there.. will take a look at that too. Thanks!

If you go this route please let us know how you go. Should be interesting!