The hack isn’t super complex, but it will require a little work (including soldering). You can’t just plug the MiFi in, unfortunately, but this hacker figured out all the little quirks and fixed them fairly easily. He hooked the MiFi up directly to the iPad’s battery for power, removed the power button (which turns the MiFi off after 30 minutes of inactivity) and replaced it with his own, small on/off switch, accessible from the SIM card slot. You’ll also have to remove half of the speaker set within the iPad to fit the oddly-shapped MiFi in.
Pretty ballsy. I like it.