My wife is always losing her phone so a while ago I wrote a little webservice that I could ping which would perform a "Find my iPhone" on her phone (logging into icloud etc) you can find the code for this on github.
Now this works great if I'm about to kick it of, but it's not very easy for my wife to do.... so I have just written the following rule:
rule "Find iPhone via Nest"
Item living_room_target_temperature_c changed to 17
Whilst I'm sure most will know what this does, for the beginners (like me!) this triggers when the temperature gets set to 17 degrees. It will perform a find my iphone, and then set the temperature back to 20!
I will be surprised if this isn't my most popular rule in the house!