A handlebar clinometer could be something to add interest to your ride, especially where the road has no indication of the degree of steepness. The problem seems to be calibrating it in the first place. You could ride miles before finding a surface that's completely level, toting your spirit level with you as a reference. It's surprising how non level even the floors in many houses are -though maybe enough for most people. It depends on your degree of QCD -ness.
When Guy and I got back from our ride on Monday I pointed out a building which leans back at a crazy angle.
There are lots like that down in the valley bottom - it is what came of building in a flood plain and not using adequate foundations!
A couple that I knew had an upstairs flat in that building. They offered me an apple, which slipped from my grasp, rolled across the table, and carried on across the floor until it came to rest in the corner of the room!
The floor in my lounge is significantly off-level. Walking across it one way feels uphill, and coming back downhill. Not enough for auto-fruit rolling though!
)
