I would think the mobile phone app would be useful only before an event - especially in locating fault structures in a given landscape. To me, these are the most useful features:

Quakes & faults near you

Liquefaction & landslide potential

Your U. S. seismic hazard rank

Your risk of quake damage

Retrofit benefit-cost estimate

I was agreeably surprised by my relatively low risk of damage, although I remain cautious....

As far as kits are concerned, I have yet to see a commercial unit that is worthwhile. DIY rules!