The Wattson, like most other smart meters, consists of two parts
1) A measuring device that clips onto the power tails coming into your electricity meter
2) A display that receives information about power usage wirelessly from the measuring device
With the Wattson the measuring part consists of a clip wide enough to attach to a 10mm power tail and the transmitter is a black box powered by 4 AA batteries. There is a button to change the frequency which it transmits data with three different periods. On the highest frequency, the display updates instantly when you switch on an electric device in your house but on the slowest update it takes about 10 seconds to update the power usage. Battery life on the transmitter is about 6 weeks on highest frequency but much longer on the slower updates.
The display is an Apple-esque white U shape that can be placed legs down with the display facing upwards (hard to read) or it can sit on one edge with the display parallel to the wall.
You can choose between showing current power usage in Watts or by annual electricity cost if you have programmed the Wattson using the provided software over USB. Change modes by rocking the Wattson.
One of the nicest features is the coloured LEDs on the back that glow from blue to red according to usage.
Aesthetics aside, the Wattson really teaches you the power usage of the appliances in your home. By programming in the correct cost per Kilowatt hour (KWh) and leaving the Wattson in cost display mode you can see how much it costs to use each device.
A fun task is to turn off absolutely everything non-essential (e.g. fridges, freezers, mains powered smoke / carbon monoxide detectors) and note the base cost of your home. Then each new device you switch on will tell you how much it costs to run for a year.
Here are some example savings I've made based on a cost of 13p per KWh
The calculation for money saved is
Money saved = Appliance rating (W) / 1000 * hours not used * 365 * cost per KWh
AppliancePower usage (W)ActionHours OFF per dayCalculationAnnual Saving
Microwave on standby20Switch off when not in use23.7523.75 * 365 * 20 / 1000 * 0.13£22.54
TV, Virgin box, CD player (on same power strip) on standby17Switch off at plug overnight99 * 365 * 17 / 1000 * 0.13£7.26
PC powered down but plugged in30Switch off at plug when not in use2222 * 365 * 30 / 1000 * 0.13£31.31
The Wattson cost me £89.95 from EcoFreak Other power meters are available for cheaper (starting from around £30) but it's a great talking point and something my wife doesn't mind having in the living room as it's stylish.