Great uses for MaxMon include monitoring elderly relatives living alone, boats in marinas, unoccupied properties and so on. MaxMon are very keen to stress the social benefits of their app and the lost cost nature of their business. Not only is the app free to download and able to run on cheap hardware, but the entire business was started with just £10k. Founder Martin Lambert is over the moon with this, saying he "burned through $50M+ of investment" in his previous venture.
More details at http://www.maxmon.co.uk/.