These sounded like a great idea, and as I have cockroaches in strange places, I decided to buy this product.
However, after sticking three to the wall as per instructions, they all fell off repeatedly. I even tried it on gloss paint thinking it may have been my matt finish paint. But they still fell, so I took them back and got a refund.
These cost $11 per pack from Coles online.
Summary The idea behind these was good, however they would not stick to the paint, so were useless.