Rtty21 has posted an Instructables project using the 555 timer to build an AM radio transmitter. By adding just a transistor, several capacitors, resistors and a 5K pot you will be on the air in the 600 kHz portion of the AM dial. While the range of this transmitter is relatively short, you could possibly interface it with a microcontroller controlled switch to work as a remote signalling device.
I got my electronics degree 30+ years ago, and I really enjoying this website. You have some very interesting projects, and I am anxious to try out a few.