The slope gradient is an essential component in the risk assessment of slab avalanches. SnowCard, Avaluator, graphic reduction method and also topographical methods such as Ski Touring Guru and avalanche terrain classifications are mainly based on the steepness of the terrain. Experienced freeriders can estimate the relevant gradient classes (<30°, 30°-35°, >35°) quite well in the terrain, but a regular ground-truth never harms anyone.
PoleClinometer
The PoleClinometer is a sticker that places bearing lines on the pole at certain degree intervals. These enable "line-of-sight inclinometry", i.e. you dangle the pole and take a bearing either parallel to the slope, up the slope or down the slope. The best way to understand how it works is to watch the info video on their website. The slogan "in any case, just Dangle It!" definitely says it all.
I think it's a great tool: It's simple, doesn't cost much, weighs nothing and allows you to determine the slope inclination in different scenarios. However, depending on the type of grip/design of the pole, it may dangle at a slight angle, which in combination with the shape of the slope can make it difficult to find a precise bearing line. I estimate the accuracy of this non-contact slope inclination measurement to be around +/- 2°. The biggest problem, however, is the wind - and a buyer review sums it up perfectly:
"Great idea, but in practice the stick moves far too much even in light winds to focus on the fine lines and get an accurate measurement ... In this case 'approximately' is just not good enough"