Just mail them to yourself. Ironically, shipped mail has more legal protections than you do. Apparently making sure other people don't read my spam mail is more important than ensuring some CBP agent isn't skimming saved credentials off people's phones. Wasn't there just an article that some major company was storing their credentials on the FS in plain text on Android?

Also, I would be tempted to wipe it, then install every cryptolocker variant I can find on it. You want my data, have at it, but I wouldn't try to do too much with it... Or just overwrite it with /dev/random. Let them try to figure out how to decrypt it lol.