If they're so obsessed with protecting their identity, they should ditch electronic devices and use paper and pencil. Write by hand and burn the paper afterward. Also, it seems like this app only works in densely populated city centers because it needs a lot of people around to create a stable Bluetooth network, otherwise your message might get stranded in a middle of nowhere, and won't get delivered in a year. Further, we never know if there's a malicious program on your phone that secretly monitors your keyboard activity or your entire screen (which I bet there's a lot of apps already doing so). What about the IMEI number? Can they guarantee the IMEI isn't embedded in the Bluetooth message somehow?