Here I will suggest essential and nice to have apps for you!

For anyone who is ever paying something in a store/shop/gas station/etc. and thinks “I believe I have a storecard of this store, but shoot, I left it at home”.
Or anyone who always carries all those cards with him just in case they are at that store.
You need to install Stocard !!!
Install it, scan all your cards and you’re done. In case a store can’t scan the barcode they can always type over the number. So you really don’t need to bring the cards with you anymore.

Mainly for Dutch people:
On the Go!
Why stand in the rain or cold when paying for your gas fillup at a gas station, while you can do all that from inside your car and only pop out to actually fill the tank?