"I'm convinced the Goodyear Grand Prix S is a major contribution to road safety." The slogan first spoken by a hapless police commissioner in the 1970s rings in my ears every time I see a gizmo that claims to improve your life chances on a bike. Reflectors on stalks, Tireflys, self-inflating lycra airbags: I've bought most of them, and left them all in a cupboard after a week.

Perhaps one of the craziest is the Reevu cycle helmet, which was sold for a while at the start of the decade. It had a little plastic mirror across the visor, which – through an arrangement of more curved mirrors running through the top of the helmet – reflected the image of what was behind you.

That's a safety feature usually reserved for drivers.

There are several reasons why gadgets like this usually end up in the cupboard, and the Reevu illustrated them all. It added bulk and weight to a standard design – something cyclists tend to be particularly reluctant to do. Because of the mirror channel on top, it didn't look cool, especially when you put it beside a standard bike helmet costing the same amount or less. And, when you started using it, it didn't work – it just kind of worked.

Many reviews and forums made similar points. The helmet had to be positioned just so to get a view of the road. The images in the mirror were too small to be useful. The mirror was too dim. It could be distracting. Basically, it was OK, but not good enough to justify its existence. Reevu went on manufacturing it for a while, and then gave up to concentrate on motorbike helmets.

But the thing is, I think the doubters were wrong. My Reevu is not in the cupboard. I use it whenever I ride. After about a week of getting used to it, the effect was revelatory. It was better than a driver's mirror because it was wider and without any in-car obstructions.

Seeing behind you becomes second nature. I can spot problems approaching long before they arrive. I bought a spare one, and a spare spare one, because I hate the loss of assurance I feel whenever I cycle without it.

After a long time in the saddle, I sometimes even find myself glancing slightly upwards as I walk along the street, expecting to see what's behind me.

Reevu tell me they plan to launch a new and improved version the year after next. If they do, I'd urge you to try it, and not just for a day. I'm convinced it's a major contribution to road safety.