Suggestion on sensors to be used for anti-theft contact detection

I'm looking for a cheap, simple and reliable sensor for long-term use and anti-theft application.

Let's say I have a big flower pot, it has an alarm. The alarm will trigger if the flower pot is being picked-up.

So far:

  1. I've been thinking about to use limit switch, but I need to redesign the flower pot's bottom to make it fits inside the pot. For long-term use, i don't think it will survive long.

  2. Proximity sensor (capacitive or infrared sensors), I have considered these sensors, but the price is the main problem and it might be overkill. I only need to know whether the flower pot is staying on surface or being picked up.

What do you think about it? Is there any suggestion?

How about a light sensor? If the pot is picked up the light level will change.

You’re going to have problems with moisture and weather generally compromising your system.

I think I’d go with a very fine wire, well “greased”, or something, which gets broken when someone picks up the pot.

Alternatively, though more expensive it would be easier to implement, a reed switch fixed to the ground under the pot and a magnet fixed to the pot. Lets you change pots easily. Can be made very weather resistant.