Am doing tech support at Cellular Machines, Inc. which makes cell-network based monitoring devices. First product is a refrigeration monitor: Freezer Alert.
My first GSM encounter was adding SMS text messaging to vending machines for a Mexican company. Components came from Hong Kong and Italy where SMS (text messaging) data communication is popular. In 2010, several executives of the vending machine company fled to the US fearing kidnapping.
That project was over and I was wondering what to do with what we had already built. I added up the benefits: low cost, small and few wires to install. Disadvantages were 12kB/sec data rate and a $5 subscription fee. A low cost Internet with no wires, no firewalls, no ISP fees.
No phone lines, No Internet needed. Uses cell towers.
I showed some product ideas to a variety of business people, a solution looking for a problem. Over half said cold storage fridges and freezers had no real monitoring. Freezer Alert was created.
SMS text alarms & logging of temperature and alarms.
We installed dozens of prototypes and found good acceptance. We made 25 more units and sold them. the pain point was "Temperature hot? Need to have a record of temperatures? (See actual log) Freezer doors open? City power failed? Get text message alarms sent directly to your cell phone. No Internet or landline telephone connection needed. A daily status message confirms operation."
Uses Standard SIM Card
A standard SIM card accesses the cell network and text alarms are sent to five cell phone numbers at cost of about five cents per message.
Log Temperatures Continually
The Refrigerator Monitor automatically sends highest, lowest and current temperature to a secure server. Check up on your freezer whenever you like. No special software required. Open a web page and you see the history. Logging periods are typically one hour.
Wall mount the control box. Run the temp sensor into the space to be monitored. Send a test message. Easy. Add sensors for door position and refrigerant leak monitoring.