A huge collection of open source apps for the Touch Bar, also if you want to make your own application, this is a good starting point.
Touch Bar is awesome
Not just because of these apps. My Macbook Pro keyboard was already broken twice - seems like quality control is nowadays missing at Apple - so I had to use a mid 2014 machine instead of mine. After two weeks without my rMBPwTB I can still say:
I was constantly looking for the Touch Bar.
Regardless of the "butterfly keyboard gate" the new Macbook Pro is a beast, after almost a year of active use I can tell you that: I love the USB-C ports, don't miss the magsafe at all, battery life is more than enough, the huge touch pad is a must have, speakers rock, performance is amazing. Everything is as close to the perfect machine as it can be with the current technology. (Can't wait the FaceID next year! #lol)
Now back to the Touch Bar: I really hope that Apple will open the Control Strip API for developers, because that would be a nice addition, but currently I am relatively happy with the Touch Bar. My only concern is that third party developers should put more shortcuts into this little screen, also in Xcode we should be able to customize the Touch Bar controls, it's unfair to have this in Safari, but not in Xcode.
How to make a Touch Bar app?
Tip: don't make standalone apps. The Touch Bar is a nice addition for existing applications, but I would not use a standalone app, unless it's a brilliant idea. Xcode 9 will help you to support the Touch Bar, you can simply drag and drop user interface elements inside the interface builder. Even if you prefer the "programmatically" way the NSTouchBar API is not a huge one, so you can easily get familiar with it.