This is a bit of a generic title but this project arose from the need for an elderly relative to be monitored for regular activity, but they didn't want anyone checking up on them so this project was born.
The project is to create a unit which plugs into a wall socket and connects to the internet via a regular broadband wifi router. A PIR sensor built into the monitor senses movement and as long it keeps sensing movement, does nothing. Once no movement has been sensed for a set length of time, say 24 hours, it sends out an alert to relatives that this has occurred and then they can decide to investigate further themselves.
The unit could be sited anywhere with known regular traffic but it was felt that the kitchen would be ideal as it had regular usage and generally meant that normal life was going on. It also had higher sockets, so someone simply falling on the floor wouldn't be able to continuously trigger the PIR even though they may be in distress if it was plugged into a socket at floor level.
For general use, an email alert was chosen as this was easily expanded to multiple recipients and didn't involve complex service contracts to be administered.
As well as plugging into the wall, the unit has a wide angle PIR sensor, runs a 24 hour battery backed clock, is configured via an SD card which also stores the email text and a configuration website. LED lights on the unit indicate wifi connectivity status (as well as power on), PIR activation, email sent warning and recessed push buttons allow the unit to be reset or to trigger a test cycle. The time is set via the internet and will adjust for daylight saving changes.