It needs to run in the background, the way the event feed works is by using URI schemas (just like iOS does app-from-app switching), so you define a schema and let your app handle it.

In my case, I used sociality://.
I post has the URI sociality://post/POST_ID_HERE.
Since I implemented URIs for this, I added sociality://profile/PROFILE_ID_HERE(/albums|friends).
So linking to those will open the respective part in Sociality.

I might go ahead and implement the fb:// schema, so Harmattan and iOS behave the same (for QR Codes or otherwise).