So the best solution to my mind would be redundancy.
First, have a UPS-based local computer where the database is backed up, which has its own internal wifi card to communicate with the ipads/ipods. A laptop with a long battery life could actually serve this purpose, if it was also backed up to the cloud regularly. I assume LCRE has already implemented the code that makes this possible.
Second, the restaurant could also have at least one ipad 3G or iphone connected to the system (or several), or use a 3G wifi hotspot device, such as these:
That way the handhelds with wifi and plenty of battery life will still work just fine if all power and landline internet connections are lost.
Let the patrons finish their meal by candle light (and backup emergency lighting for kitchen, bathrooms, hallways, etc.) and check out via the wifi/3G connections with no problems.
This was a question I presented almost 5 months ago, with that exact suggested resolution (an in house server that maintained contact with a central database but could function as a stand alone if needed). A bit more regarding start up cost but would help with unforeseeable outages.
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