I'm wondering how popular it is as i've never heard of it or ever seen anywhere offering it.

Maybe its only popular in Germany, its almost like asking if all currency in the world can be GBP as its popular in the UK

They are active in NetherlandsBelgiumUnitedKingdomGermanyAustriaSwitzerland

and a lot of online shop already uses this because you can pay with the securitytools of your own bank (digipass....)

A lot of shops implemnet this already?

See for more info: https://www.payment-network.com/deb_com_nl/integration/list/summary_nl

Or implementing OGONE worldwide payment system it also a very good alternatif:http://www.ogone.com/

We hear nothing about this issue