When I had my nursery, I used a Watchdog remote sensing system, and it was excellent. Each greenhouse had its own wireless monitor, and in the house I had the base unit. The base unit displayed the current temperature in each house (updated every couple of minutes) and, if set to do so, could sound an alarm when the temperature went outside predetermined boundaries (both high and low). As it happens,. I still have the system (5 monitors and the base unit) and will be happy to discuss selling it for half of what I paid (it was only used for the last 2 winters I was in business). Even that isn't cheap, though. These things have quite a long range and are built to last. Ellen -- Ellen Hornig 212 Grafton St Shrewsbury MA 01545 508-925-5147