Raspberry Pi

2012 - present

The Raspberry Pi is a credit-card-sized single-board computer developed in the UK by the Raspberry Pi Foundation with the intention of promoting the teaching of basic computer science in schools.
(taken from Wikipedia)

I currently own four Raspberry Pis, which are employed as follows:

All the Pis periodically log a few variables to cosm.com (internal temperature, CPU load, etc), from which I can produce charts, query for time series data, etc.