A match made in heaven: Any web-enabled Arduino... ESP8266's work especially well... and the amazing, free, service from IfTTT.com
This post to announce a "getting started" guide. IfTTT ("If This, Then That") IS extremely cool... but so cool that the possibilities seem endless... and as a result, finding a place to start is a bit of a challenge.
The tutorial at...
... will take you, step by step, in a good sequence, though your first IfTTT project. At the end of it, you will have an Arduino with a SPST switch to pull D4 to ground. When you do that, a message will go to the nice people at IfTTT, and they will send emails to whomever you've set the recipe up for. (I believe it can do SMS's just as easily.
The SPST on D4 is VERY crude... but changing what causes the emails to be sent is trivial. I wanted the demo to have as few distractions as possible. The button could be replaced with a temperature sensor, if you wanted to know if vacant premises were experienceing a failed heating system, for instance.