Reduced from £112
The marvellous Renschler Solario is a tiny Solar-powered mini accoustic variometer, acclaimed as the ideal first vario, but also as a perfect back-up instrument that you will never want to sell. Great pilots like Bruce Goldsmith have chosen to fly only with a Solario and a GPS when competing, so you know it does the business.
The Solario used to be unique, but now there are cheaper alternatives. I have flown with most of them, and they don't offer the same quality audio as does the Solario. I think it is the best - if you can afford the slight extra cost.