Soil Thermometer

Hi All. been meaning for ages ,last spring actually to buy a soil thermometer. I had a look on the web and anything from basic £4.95 up to whatever you want to pay.
I think I would prefer a digital one just as it would be easier to read and one with a long probe.
Anyone got any experience with using one or can recommend a thermometer to buy. They may not give the most accurate temperature of soil unless you get a top class one but should give you an idea if soil is too cold to plant.