Quantity   Component name
1 × VTech DM1111 Baby Monitor, TX & RX
1 × Seeed Studio XIAO nRF52840 BLE enabled microcontroller, running CircuitPython
2 × 3.5mm TRS/TS jacks Either TRS or TS will work - only need two leads
1 × 3.5mm cable ("aux" cable) Again, either TRS or TS will work
1 × Tatoko DC coreless vibration motor (3V) Any haptic motor that accepts 3-5V DC would be fine.
1 × MOSFET based DC motor driver Should be able to handle 5V DC. (probably overkill, you could likely just use a transistor + diode)
1 × Large hair elastic Or any comfortable bracelet that can have the motor sewn to it.