Radio transmited devices have come a long way since they were first introduced. If that really was a wire it was an ancient one from the 70's and considering all the technical applications the president could use I don't think he'd use one that size.

The FBI doesn't even use devices that big. But this wouldn't be the FBI's technology - it would be your secret services. Much more advanced than your regular law enforcement devices because your CIA and other agencies don't let the FBI have the same technology for the simple reason the FBI have to reveal everything they use.

Then consider the position. Surely there's better areas of the body to hide it, if say the allegations are true. Let's entertain the thought that yes he's wearing a wire. Surely the front of the body would be the most appropriate place to hide it?