I've never been to Tokyo, but I hear they have a bit of a problem with crowded subway trains —a fact brought up countless times as I traveled from Gizmodo HQ to the convention centre during CES. Needless to say, I heard "It feels like Tokyo in here" more than once. Thankfully, these packed trains did not result in a shameful groping of my buttocks. In Tokyo however, this can be a serious problem.
The portable subway strap is designed to show female passengers that your hands are occupied —thereby reducing your chances of being falsely accused of groping. Apparently, the 525 yen ($5) product has proven quite popular with commuters. Although the train above seems to have a much more awkward situation brewing. [Product Page via Pink Tentacle]