Dan Jolley 
Alex Unlimited, Volume 2: Split-Second Sight [PDF ebook] 

America has always been rife with "mediums, " but now it looks as though one girl is the real deal: Amy Titus — a spacey, New-Age hippie chick from San Francisco. If Amy really can contact spirits, then the government has either a major ally or a potential threat to national security. When Amy disappears mysteriously, it’s up to teen secret agent Alex to track down the missing medium. Is Amy what she appears to be? And can she really communicate with the parents whose death orphaned Alex so many years ago?