Download install and relaunch updates for your Mac/Cocoa app

Question

I was wondering if anybody has any suggestions for how to install and relaunch your updated app when you download it from Internet!

There are tons of apps that get their new versions and install and relaunch themselves but I don't know anyway but to use a second updater app to do this.

Any suggestions?
Cocoa or version specific or appstore specific suggestions welcome, too!

Basically there are 3 steps:
1- detect and download the update (easy enough)
2- replace the older app from /Applications with the new one
3- launch the new app

Answer 1

Use Sparkle- https://github.com/andymatuschak/Sparkle