There's little doubt DIY Kyoto knows how to market. From its unusual company name to that of its main product, Wattson, it obviously has a flare for creating interest. Wattson is an energy meter, which will show you how much electricity you're using in watts and how much that'll cost you over a year, if you run with the same usage.

Like most home energy meters, Wattson consists of three devices: a small magnetic clamp that fits around one of the mains cables coming into your domestic meter, a battery-powered transmitter that attaches to the clamp via a short cable, and a display unit that can be plugged in anywhere within range of the transmitter, or used on its rechargeable battery if you want to roam around, checking the power usage of different appliances.

The display unit is unusual in design. It looks a bit like the bridge brick from a child's wooden train set, though this is deeper and made from black and white acrylic. Alternating banks of blue and red LEDs underneath give you a quick indication of the power you're using; they move from blue through purple to red as power consumption increases.

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There's no LCD display or meter and, at first sight, you might wonder if the purple glow is all you get. In fact, DIY Kyoto substitutes any LCD with a large, red, five-digit alphanumeric LED display, which shines through the white top of the Wattson.

As well as displaying the current usage in watts, a quick tilt of the display unit backwards changes the display to pounds for a few seconds. This cost is worked out using a default electricity unit cost of 13p, but this can be changed to reflect the current rates of your own supplier. The pound display is only a spot cost, anyway, so unless by some fluke you're running at your yearly usage when you check the display, it won't be of much value in predicting your bill.

However, Wattson can be connected to a PC or Mac via the supplied USB cable and, with a quick software download from the DIY Kyoto site, you can enter your own values for day and night rates and a standing charge. It wouldn't, though, cope with the dual-tariff day rate, separate night rate and standing charge EDF uses in working out our quarterly bill.

Once you've been running Wattson for a few days, you can plot your electricity usage and quarterly or yearly usage rates are then likely to be more accurate.

We couldn't find Wattson for less than £149.95, which we think is on the high side, even with its rechargeable cells and memory. More functional-looking meters, with similar or better specifications, can be had for less than £50. Few have the storage or PC analysis, though, and none has the coloured LEDs underneath. If the design appeals, Wattson will no doubt create its purple patch for you.