Very good developments!
They updated the Kobo app in the Android Market (Google Play whatever) on March 23rd 2012. It now works on the Nook Simple Touch by Barnes and Noble.
This is a video showing off the newest version of the Kindle app running on the Nook SImple Touch. It’s not the version that lets you email to Kindle Documents. That version won’t come becuase it requires Android 2.2 and up, and the NSE is stuck on 2.1.
The video ends abruply because the browser crashed, and my wife came home and I didn’t want to restart.
It doesn’t look like he’s running the eInk refresh hack in either video. That would make a difference with the new Kindle app UI.
Mike Cane’s xBlog 
I can’t get the current version of the Kobo app (18 June 2013) to fully work on the NST. Has anyone else tried this ? (I can download books, but it fails to open them).
It could be due to whatever the app requires in terms of APIs not being present in the older version of Android the NST uses.