The Vista-20P can handle 48 zones without zone doubling. This job is nowhere near the panel's limit, Crash. If the gentleman wants Internet and GSM, it's one of the few systems that meet his requirements.
To do it that way he'll need a temperature sensor with remote probe that requires no power. I used one from Grainger to activate the exhaust fan in our generator room. I don't recall the make/model but it was less than $100 and it worked well for over 16 years. The unit had a flexible, copper tube with the probe on the end.
The problem with the unit, as you noted, is it requires power. The gentleman indicated he wants to go wireless. It can be had with a M-001-0081 high temperature probe (32 to 299 F). Most of the Winland's mechanical temperature sensors have been discontinued. The one mechanical unit that handles high temperatures is the MTA-1. It's limited to 100C (212F) though.
We get a lot of orders for the 2- and 4-zone programmable models, mainly from food storage facilities and the like.