I've been running my Raspberry Pi server for the past 9 months now. It's been a tremendous success running server / device monitoring & downtime alert software called PHP Server Monitor. As the name suggests it is written in PHP which makes the software very easy to customise and tweak. Currently, PHP Server Monitor is configured to send emails when any one of the devices it is monitoring fails to respond. It also sends an email alert when the device becomes available again.
Here are just some of the devices being monitored. I have obscured IP addresses for security reasons.
Another piece of software running on the Raspberry Pi is 'thermd', a 1-wire device logging and graphing tool written in Perl. I have 1-wire temperature and humidity sensors dotted around my home and garden, monitoring freezer / fridge temperature, front room, upstairs, heating system temperature. Outdoors, I have data from outside temperature sensors, greenhouse, propagator, cold frame sensors. Coupled with a rain gauge and light meter, I have plenty of data points being made available across the Internet to my iPhone wherever I am. The home automation software also hooks into this data to make decisions on whether to heat the house, water the plants in the greenhouse, turns lights on etc. The Raspberry Pi is switched on 24/7 and is powered by the sun.
Here is the graph produced by thermd. This is just displaying temperature sensors located outside.
Solar energy is stored in large batteries and a 12V feed runs via a multi-way cigarette socket. The Raspberry Pi USB cigarette lighter adaptor is plugged in to this multi-way adaptor. You can find 12V USB chargers from most places, but I found this one by following this link to Raspberry Pi Power Supply