We got a water and temp monitoring system when we did the winter away. It dials out on a phone and sends you a message.
I had a Verizon land line and when I asked if they had a reduced service (for a reduced monthly fee), they said no. So I put the line line on vacation hold and went to the Verizon wireless store and bought a wireless home adapter, which is basically a cell phone in a box that you plug a wired phone into. $20 a month for the added line. I plugged the monitor into that It worked great.
It worked so well that when I got home I dumped the land line and got a Panasonic base station wireless system and I'm using the home adapter for my home phone.