In my opinion I would only bother if I had a more expensive and desirable key-less car. Even a low mileage, high spec, top condition R27/200/Raider is only going to be worth good money to a collector or enthusiast and I don't think these people are the ones to be ordering cars to be stolen.
Personally if I were adding extra security to a car, it wouldn't be the key less protector - at 145 euro I'm not convinced how something that goes over the battery can protect the car, especially when a high number of thefts at the moment are drifting away from key cloning and people are now breaking in for the keys anyway.
I've looked in to security a little bit when I've toyed with the idea of other cars and I like the idea of the Autowatch Ghost - Basically the car can only be started when you put a sequence in (that you pick) on the buttons in your car. For example: Get in the car, press 4321 on the radio and then the cruise control button on the steering wheel before the car will start.
As said above, the pouches are meant to work well and are only cheap from Amazon. You could get one of those for peace of mind.
I've seen more car thefts at the moment where people are breaking in the for keys. I know people say they take the keys to bed with them etc, but IMO it's really not worth the hassle. If someone is willing to break in to my house for my keys, then I will leave them in plain sight and they can take them and the car - My girlfriend's and my safety is more important.