I thought some of you might find this interesting.
My sense is relatively new (about a week) and it had not detected my downstairs air conditioner yet. While looking at the graph I could see the A/C kicking on and off but I noticed something I thought strange, the downstairs AC would spike anywhere from 1 to 4 times before it would actually start. Sure enough when I got home from work last night, capacitors for the compressor blew. No more cold air.
I am assuming this multiple power spike with failing to start was it about to die. I will watch it the next few days after I fix it to see if I am correct and this behavior goes away. If it does go away, there is the interesting possibility that the Sense could warn us of devices about to fail.