When I was sent this article, I must admit to being very sceptical. ‘Magic’ solutions and miracle cures have usually turned out to be snake oil of no real value.
Still, Kew Gardens are endorsing the product and the science, as far as I can judge seems sound. Some 14 years on since I was sent this article I’ve found out that Kew gardens has not endorsed the product since 2006 and the science behind it generally not accepted.
I don’t think you can still buy the products and if you could I cannot recommend it so I have deleted the content.

The battery operated Vi-Aqua Plantmate is designed to be used in small gardens where the electro-magnetic field can penetrate up to 55 litres of water.
Here we see it being used with a watering can.
The larger Hosemate version is designed to be used with a hose.