Facebook app questions..

hi guys

Looking to get a facebook app created

Firstly how difficult is it to program an app that does something simple enough

Basically I want it to keep a track of information that a user enters and post messages on their wall at certain times

I guess it would be db driven!

Plus their friends would be able to see their info that they have entered

So that's the first question(s)

Second is if you are the owner of the app can you pull much information about who is using your app, ok it might say 1,010 people are using app but how much info can gain about the user base?

Can you message the user base?

Ie what is the best way to monetise an app if at all?

Can a facebook app be created that will integrate with android devices?

I know that farmville finally did this with their iphone version of the game that would pull your farmville info, so could this type of thing work with android?

Last question

How expensive to code an app for android, again quite simple time management tracker type of thing

thanks for all and any help as usual you guys are the bomb!