Not a problem if you use iOS9: <a href="https:&#x2F;&#x2F;labsblog.f-secure.com&#x2F;2015&#x2F;09&#x2F;09&#x2F;apple-ios-9-security-features&#x2F;" rel="nofollow">https:&#x2F;&#x2F;labsblog.f-secure.com&#x2F;2015&#x2F;09&#x2F;09&#x2F;apple-ios-9-securit...</a>
For Android, you can root it and disable USB host functions when locked.