The pressure mats generally don’t come with the radio piece that you need to integrate with SmartThings. So you can buy pretty much any pressure Mat you like and then attach it to a Z wave device, typically a contact sensor with dry contacts.
The Following thread discusses how different people have done that:
If you’re looking for just the Mat, united security is a popular brand. These mats are used by both stores and, for example, as doorbells for houseboats. So you’ll find them sold in a lot of different places.
Some third parties will sell them through Amazon or Sears, but the prices vary a great deal, so shop around. Also read the descriptions carefully, as the sizes vary a lot. It’s pretty common to stick one underneath a welcome mat, but you want to be sure that where the person stands will actually trigger the mat.
This one is about the same size as a sheet of typing paper, a little longer. I’ve seen the same size sold for everything from $20-$125, so again shop around.
This one is bigger, more the size of a welcome mat, but the problem is it’s a 60 pound press which won’t catch a lot of little kids. So as always, turn comes down to the specific needs you have.
And here’s the perfect example of why you need to shop around and also read product descriptions very carefully. This is the welcome mat size, but with a 25 pound press. So that’s good. But this particular vendor has priced it, in my opinion, pretty high.
I think the United security brand is popular because it’s very easy to wire to something else, and you can buy just the mat, it’s not prewired to an alarm.