my andriod phone came with a bubble level than can be set to % of slope, but without an actual level i have no way of knowing if it is accurate. I read some where that some carpenter compared it to a really expensive digital level and that it performed just as well, but I find that hard to believe. Like Erik said, a small bump would make a big difference.
I got access to the forum last night, and I really think that will be a great resource to answer any questions that come up as I work on the techniques. That eliminates just about all of my frustrations/concerns about my experience.
Would it if you mashed it into the ground a little? How do the "breakmeters" ovecome this issue. I assume they don't weigh 20lbs and are the size of a pizza. I would think if you played decent greens, didn't set it on an obvious pitchmark and did your level best to press the phone a little down below the bumps, you would get something pretty close to another method. Stretch's clinometer suggestion seems fairly sound to me.