best app to forget anything or twice to buy

Purchase Intention:
As my girlfriend and I often buy separately after work it seemed many times before, that was bought twice. Looking for an app with which I can accomplish that shopping lists are always fully up to date, I came across several these is the best.

Benefits:
- Several receivers can handle the same list
- Multiple lists can be applied (Metzger, discounters, market, drugstore, pharmacy, etc.)
- Easy handling
- Quick update has reached when a change to another mobile phone occurred
- Appealing design

Disadvantages:
- 2 months ago after I bought me it was to have free :(
- Harmonization of lists will only work as long as the devices have an internet connection (otherwise not possible !!!)

In short:
The app I was looking for and I like to get back the money would also spend.