Basically any device or thing that has an internet connection can publish information about itself so that it can be consumed externally. For example if you had a BeagleBone microprocessor monitoring temperatures and you wanted to share those temperatures with other people or machines on the cloud, you could do it easily with dweet.io. It's basically a really simple pub/sub platform.

A few examples:

- Public swimming pool temperature

- Air quality information in city

- Traffic light status

- Train GPS position