Camouflaged AAA battery alarm device

This project is to create a wirelessly activated alarm device that is camouflaged as a AAA battery. Brief: Two pieces of hardware - an "alarm unit" and a "control unit". Alarm unit description. It must: • be precisely the size and shape of a AAA battery. • behave exactly like a rechargable AAA battery • supply at least 1.2 V to the outside world, through standard AAA battery contacts • be able to be recharged via a standard AAA battery charger (charger type you may choose - NiMH, LiON, etc) • be fully self-contained with all electronics • contain a buzzer / speaker • contain a wireless receiver and antenna • Sound an alarm when a specified wireless transmission is received • continue to sound until the transmission stops • have battery life of at least 6 months when "listening". It is acceptable for the device to "sleep" and wake up at regular intervals (say, 10 seconds) to check for the transmission • have very low manufacture cost Control unit description. It must: • contain transmission electronics to issue the wireless signal for the Alarm unit to sound • have on the enclosure a toggle button to turn the wireless transmission on/off • be easy to toggle • be in an enclosure of reasonably small size, but this is not a tight restriction. I would probably use an off-the-shelf enclosure. • have a user-replaceable battery (don't care what type) • have very low manufacture cost Project Milestones - all milestone apply to BOTH Control Unit and Alarm Unit • Electronics Design • PCB Layouts • Enclosure designs • Prototypes fabricated • Firmware written • Prototype testing • Further system updates / changes • Design & tooling for short manufacture run • manufacture run (prob 100 units)