I am looking for ideas of something to use as a bumper sensor for the small wheeled robot I am designing. This sensor would serve as a backupfor the optical primary sensors. I could, of course, just use a couple of switches with long actuators, however I would prefer something more elegant. Optimum would be some sort of narrow strip (<~.5") about 3.5" long that I could wrap around the front of my chassis which outputs a digital signal when it comes in contact with something. I am open to other suggestions as well however. Cost is a big issue, I do not want to pay more than a couple of dollars for such a device. Thanks.