Methods of Antenna Detection

I've seen antenna detection done where a pull down resistor is built into the antenna to detect if an antenna is present or not. If say I was using an off the shelf dipole antenna (no built in resistor), what would be a good alternative way of being able to detect if that antenna was connected or not? It would be connected to an N-Type (or maybe SMA) connector without a mechanical antenna detect, so I'd be looking to do this discretely.

an inductor to ground will do it

Depends on what point is desired. If you need to detect antenna connection to a device like a transmitter, use a SWR indicator or a reflectometer. A matched antenna will generate a low SWR response, a disconnected antenna a high SWR output.

Another problem is to detect antenna presence in a remote location. Again antenna matching is important but a radar-type device is needed.