Use Arduino to transmit signal to a vibrating pager
To do SMS through a GSM shield like https://www.arduino.cc/en/Main/ArduinoGSMShield with a dataplan, and the device should be accessible anywhere you can get reception.  With a wifi shield like https://www.arduino.cc/en/Main/ArduinoWiFiShield101 you could make it work within your wifi network.

Sparkfun's sales guide at https://www.sparkfun.com/pages/wireless_guide indicates there are a few bluetooth modules that reach 100m, so if your range is less than 100m, bluetooth is a possibility.