The initial design for a sensor mote puts three temperature sensors together with an Arduino and short-range radio module. The following is the parts list for a single sensor mote:

• Arduino Uno -- £18.50
• Arduino XBee shield -- £12.10
• Arduino Series 2 2mW XBee radio module -- £17.50
• Arduino prototype shield -- £10.40
• Mini-breadboard -- £2.00
• 3 x DS18B20 one-wire digital temperature sensor -- £11.70
• Battery holder -- £1.20
• Enclosure (waterproof, resealable food box) -- £3.50

A total of £76.90 (+ VAT) per sensor, not including assorted wires and resistors. [UPDATED 11Jul2013: added cost of enclosure]