"The payoff for this type of robbery is just too small to draw in a lot of innovation"
Sure, nobody would do a startup with this market in mind, but if it is cheaply and reliably available, I bet people would start using it, just as people started using bolt cutters to steal bicycles. Also, if one had reliable tools to filter for low risk victims, it would statistically become more profitable to rob people. If you can expect to take an average $10 from ten people before being caught, fewer people would take the chance than when it is $10 from about 100 people (humans do not always make judgments that seem rational. For an example, see http://www.scientificamerican.com/article.cfm?id=stats-show-...)
Sure, nobody would do a startup with this market in mind, but if it is cheaply and reliably available, I bet people would start using it, just as people started using bolt cutters to steal bicycles. Also, if one had reliable tools to filter for low risk victims, it would statistically become more profitable to rob people. If you can expect to take an average $10 from ten people before being caught, fewer people would take the chance than when it is $10 from about 100 people (humans do not always make judgments that seem rational. For an example, see http://www.scientificamerican.com/article.cfm?id=stats-show-...)