This is an interesting article from WIRED about the many and varied uses for Twitter – thanks to numerous apps that have been developed. It begins:
Thanks to its open-ended design and a thriving user community, Twitter is fast outgrowing its roots as a simple, easy-to-use messaging service. Enterprising hackers are creating apps for sharing music and videos, to help you quit smoking and lose weight — spontaneously extending the text-based service into one of the web’s most fertile (and least likely) application platforms.
Hardware hackers have set up household appliances to send status alerts over Twitter, like a washing machine that tweets when the spin cycle is through, or a home security system that tweets whenever it senses movement inside the house. Others have incorporated Twitter into their DIY home automation systems. Forgot to turn off the lights? Send a tweet to flip the switch by remote control.
And along the same lines, Search Engine Marketing Group lists 10 Examples of Creative Twitter Uses. These range from checking your laundry to wine tasting!