First, here's an interview from MTV with Shailene Woodley about the box and the significance of Tris's divergence.
Next, some info from Lionsgate explaining some of the production value of adding the box to Insurgent's story line.
Lastly, we also learned today that Insurgent will be rated PG-13 for intense violence and action throughout, some sensuality, thematic elements and brief language. The movie will have 158 minute run time (2 hours, 38 minutes! 19 minutes longer than Divergent!)