You can set off your delayed bombs at great distances.
If you have line of effect to your delayed bomb, you may detonate it earlier than its preset time by making a DC 20 Intelligence check; the DC increases by +1 for every 10 feet of distance between you and the bomb.
Pathfinder Roleplaying Game: Ultimate Magic. © 2011, Paizo Publishing, LLC; Authors: Jason Bulmahn, Tim Hitchcock, Colin McComb, Rob McCreary, Jason Nelson, Stephen Radney-MacFarland, Sean K Reynolds, Owen K.C. Stephens, and Russ Taylor.