"The answer quite simply is to leave your phone at home."

Not really feasible for most travelers. Try exporting your data, encrypting it and sending it to the cloud. Factory reset the phone, cross the border, arrive wherever, download, decrypt, import. Rinse and repeat to go home; the Canadian leos are using the same loophole for extending fishing expeditions.  I expect that there will be an app to do this available ... now. Get in on the ground floor.