Selected a microcontroller platform for my prototyping. My criteria were:

• Rapid iteration
• Connects to smartphone
• Rechargeable battery
• Accelerometer and LEDs built-in

Given all that, I've chosen the CircuitPlayground Bluefruit. It supports Circuitpython which is perfect for rapid iteration (no need to compile every time), and Bluetooth so I can control it from my phone right off the bat. Also supports using a LiPo although doesn't have a built-in charger - no biggie, I have a couple of external LiPo chargers lying around.

Initial purchase is gonna be in the ballpark of ~$90 CAD which is pretty good for janking things together with no optimization! The sleep mask is ~$10, two Bluefruits for ~$65, and a couple of LiPos for ~$7 each.