I recently developed a program called Watch Tower. This turns an Android phone into a wireless surveillance camera. The phone takes images periodically and sends them (via HTTP) to a computer which can accept files. It can use either the cell phone's data plan or Wi-Fi to send the images.
Watch Tower requires setting up a receiver program on some computer, but this is very easy to do. This can be done on Windows, Mac or Linux using any web server and some trivial cgi scripting. Details on how to do this are also on the Watch Tower page.
The entire source code is available under the GPL.