That attitude indicator looks nice but is also quite expensive. Today I purchased that thing I put picture of and basicly it works. I made also a quick video and put it here as soon as I get it on the youtube...
But you can get a thing that gives more data and can be used in more ways that just that uphill or downhill info. First I need to purchase that meter and make some tests with it.
Boat inclinometer - - ComNav
Its called boat inclinometer and it has two "bubbles" rough and fine scale. I think that will be suberb on that purpose.
Problem with that simples scale was that it tell for sure is the hill big or small but not the "scale". I tried to find that kind of inclinometer but they can be only found at boat shops. Price will be about 20$.