A wifi password sharing app has to do the following 3 things at a minimum:
- Allow sharing (and unsharing) of passwords with friends
- Sync updates from the cloud
- Show appropriate notifications (especially with a user must take action)
And there are other apps out there that can do variants of these functions. However, the two main ones that I know of have two major flaws:
First, they only support Facebook and I don't know anyone that has a perfect intersection of Facebook friends and people they share their wifi passwords with. There's no reason to limit sharing to any specific social network. Facebook and friends in general are not central to the solution, only sharing is key.
Second, these apps must be storing the passwords as unencrypted clear text in their databases by design, or the passwords are encrypted in a manner that their servers can decrypt for client devices. This is a risky approach, and a lazy design. Only the client devices need to be able to decrypt shared passwords, not hackable servers that only broker between devices.
You should expect better.