I've been using my Omron for about six months. It has its limitations but it also has its strong points. It takes some doing to get the stride set right. I finally tested mine against a track and finally have it close to accurate. The mechanism that makes it work is very sensitive...that's why it picks up movement when you wear it all day. I only wear mine all day if I'm working on the # of steps. If I'm using it for a walk, I don't put it on until I actually start the walk. It doesn't start counting aerobic steps until after a set number of minutes -- I think ten. That's why it didn't pick up your jump roping.
By the way, I had lost the manual for mine and found it online. So if you forget how to change a setting, just do a search on pedometers.