For something a bit more specific to your sport you can turn on appropriate comments for Mountain biking, Downhill ski-ing/snowboarding, avalanche danger, Water Ice (WI) and Scottish Ice climbing.
How Steep can be a bit of fun so you can boast to your mates about just how steep that gnarly run was or it can be dead serious; that slope is steep enough to avalanche.
There is a free version (HowSteep Free) which displays ads and a pay version (HowSteep) without the ads;
Get it in the Android Market.
Be prepared for it to be less steep than you thought when you were looking down (or up) the slope.
Though the angle of the slope shown is accurate this app is just a bit of fun; Smallbouldering Projects take no responsibility for persons misinterpreting the comments.
In particular avalanche prediction involves much more than the degree of the slope.
Ski or ride at your own risk.
If in doubt about the danger consult a professional.
Please report any bugs or issues to email@example.com. If possible please include as much detail as possible about your phone, what happened and when.