[ogihsgnx] Push to antenna

Create a NFC device whose antenna becomes connected only when the user pushes a button on it.  This seems easy and possible to do cheaply.  One possible application is jewelry that can be used for identification or authentication via NFC, but the user doesn't want it to be constantly scannable, identifying the user remotely or without the user's permission.  Of course, if applicable, its security should be combined with something the user knows (e.g., password) in case the device falls into enemy hands.