How do you use those devices and at which points?
I'll let GMs who are currently running and/or prepping to play the adventure speak to specific useful points in the story itself, but from a designer's perspective, those tools are excellent for providing info to PCs when they get stuck or missed an important scrap of information.
Reeeeally wish your PCs hadn't have failed that Perception check for that one vital little clue? Have that thing start heating up in their belt pouch, or vibrating when they set it on the table or try to use it the first time. Fun stuff. =-)
And while the haunts have no background, that shouldn't stop PCs from discovering the means of their destruction either through the use of the planchette or the optional "rapping spirit" rules in the haunts sidebar.