The Photon is a neat little embedded device a bit like the Electric Imp I played with a while back, but a bit cheaper to get started with. You write C code in your browser and the program is deployed over WiFi to the device. The hardware is very like the Arduino. The programs can communicate via the cloud using web requests and there are also bindings for If This Then That.
To be honest, I've not done much with it, but number one son has had a play and things it's quite neat. The only concern I have with these systems is that you are a bit dependent on the cloud backend. I've got a collection of cloud enabled devices that are now just paperweights, and I worry that things like the Photon might go the same way. Having said that though, for the price it is a lot of fun.