I have be working on an Arduino compatible board with several sensors and a socket for the nRF24l01+ - mainly because I was tired of wiring by hand. Im on the second prototype pcb and have most of the bugs worked out of the hardware.
It has I/O for IR temp, 1 wire temp, AC current (openenergrymonitor.org circuit), Humidity, IR in and out, logarithmic light sensor and a socket for a display. Its designed to be small enough to fit in a single gang electrical box.
I have been writing code in nodejs using mongo to log everything and graph it on web pages with a Raspberry Pi.
Its turning out to be cool enough that I would buy it - so I thought maybe someone else would be interested also.
If anyone is willing I have started a blog http://blog.level451.com/2013/11/somewhere-to-start.html with more detail and would love feedback and suggestions before I finalize the hardware. The blog is obliviously a work in progress.
If anyone is interested I can show you the webpages it creates.