What are you looking to do with the WiFi?
We have a Sprint MiFi 2200 and use it all the time in our AS when at campsite. I usually keep it plugged in to the charger and leave it on all the time. Works great for us -- we have a MacBook and an iPad. Both can be connected and share the MiFi at the same time.
If you want WiFi while rolling down the road, the MiFi should do it for you, too.
I also have a Linksys wireless router in the trailer that I keep plugged in to the Inverter outlet. We use that when we are towing. The last thing I do before we pull away is turn on the inverter circuit, activating the router. I have an IP camera mounted in the rear window of our trailer using velcro, also plugged into the inverter circuit. It is set up to use the router in a local network. I use my iPod Touch in the tow vehicle to connect via the local network to the camera and have a really cool rear-view camera in the TV. Very handy for backing up and just monitoring traffic coming up behind us.
I'm going to post a story and pictures of the setup in the forum this weekend.
2010 25' International Serenity
2010 Toyota Sequoia
WBCCI 2515, TAC VA-9