Hi, I need to make cheap DIY bracelets like these: Amazon.com: BOND TOUCH Long Distance Touch Bracelets for Couples - Stay Connected Anytime, Anywhere - Unique Relationship Gifts with Real Time Messaging and Customizable Colors - Pair of Bond Bracelets : Electronics
They need a microcontroller, a radio module, a battery and a vibration motor.
What's the smallest microcontroller I can utilize? What radio module to use? I'm thinking Bluetooth, I'm fine with 10m range, there will most likely be a direct line of sight. I'm not sure about Bluetooth vs 300/400 MHz radio module power consumption. It better be as little as possible. About batteries, I will either use a CR (button cell) or a small Li-ION/Li-PO pad (better, of course, CR).
What do you guys think about this project? Can it be made for, say, less than $40?