I notice more interest here in this topic. Besides the monitors (mostly geiger counters) which are typically offered on ebay. I will mention this company: Aware Electronics Corp. Radiation Monitors for PCs Aware electronics has been selling microcomputer compatible ionization detectors for a long time. Evidenced by the fact that the are primarily compatible with serial ports, which have all but disappeared from portable computers. I bought the RM-70 years ago and have learned a lot from it. Mostly about radon, 'nuclear fleas' which accumulate short-lived radon decay products and you can collect from your (conventional CRT) television screen. Ocassionally you will find something else which is 'hot', the most likely perhaps being orange or brown-glazed pottery. If you are very unlucky and a nuclear power plant near you is releasing, you could immediately know that as well. But for the most part, it would be a tool for learning about environmental physics.
