I've just come across Mango - a piece of software that may be of interest to me in my house monitoring experiment:

Mango, open source M2M

Welcome to the home of Mango, the world's most popular open source Machine-to-Machine (M2M) software (also known as Industrial Control, SCADA, HMI, or domotics). Mango is browser-based, Ajax-enabled M2M software that enables users to access and control electronic sensors, devices, and machines over multiple protocols simultaneously. Easy to download and install on many platforms, Mango provides an interface with which diverse data sources can be created and configured while providing downstream management of user access, alerts, data logging, and automation.

[From Mango, open source M2M]