[Mhkabir] built an irrigation system that communicates by text message. The concept is simple, sending a text message to the system will cause it to switch on the water pump.
Many times we see text message manipulation via the Internet, or using a GSM module. But in this case an inexpensive cellphone is used as the communication interface. The vibration motor has been removed and those connections are monitored to signal incoming messages. Wire leads were soldered to the keypad contacts which allow an Arduino to send out text messages when there is a problem with watering. This isn’t an iron-clad system, as any incoming message will trigger the system and outgoing messages are limited to saved drafts. But a bit of creative programming and we’re sure more functionality could be squeezed out of this hardware.