using blockchain.info api, it would take really a month to get an API key 
my two applications got rejected recently
I don't understand why they are so restrictive about their API, but if you really need one to work with, use block.io, i like them because it is really easy to use, easy to generate and manage accounts, and they support bitcoin litecoin dogecoin.my two applications got rejected recently
I didn't tested the others but i plan to do it soon.
Talking about these APIs is there a website who tracks them ?
You do not understand ?
Because it costs them lots of money and ressources to maintain the API up, and to answer all the technical issues for the API users.
Why not just make an API like that one, for free and you will have an idea of its complexity.
Block.io sucks.