The authorities are already aware of where these people are, The target audience here being only those who feel threatened, or scared, to know these people might live nearby, But that chance has always been there.
I feel this app can only serve to boost paranoia within the public mind.
The same people who are staying inside, petrified of catching swine flu and dying from it.
So are you really saying that you wouldn't change their route to school, given that there is somewhere at least 0.8-1.5% chance of this sex offender reoffending with a non-family member? (Assuming a reoffence rate of 8-15%, with 10% of those people offending with non-family members)
Yes, which is why lottery tickets are largely just an unfair tax on the poor and uneducated.
I don't play the lottery for similar reasons I don't bother finding out the personal criminal history of everyone living in my town - waste of time. YMMV
How many sex offenders have offended random school kids walking to school past their house? I'd say it's likely to be miniscule.