Is it permissible to touch someone of the opposite sex with an object (for example: to get their attention)?
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The prohibition only applies to "derech chibah", so even without an object it would not be forbidden, though in practice it would not be recommended. However, with an object wouldn't be a problem.
See the beginning of this Hakirah article by R.Y. Henkin: http://www.hakirah.org/Vol%204%20Henkin.pdf
While poskim argue over what a handshake is classified as, they agree that something that isn't derech chibah is not forbidden.