It would be difficult to prove obstruction of justice. The parameters for a prosecutor to charge needs to prove that the person knowingly and willingly deleted the evidence while he was being investigated. If its an app that automatically scans and deletes stuff its neither willingly or knowingly destroying evidence. Also, it's only 6 months and a misdemeanor instead of a potential whatever you were charged with.
It would be even more difficult if it were a full factory + disk rewrite/wipe or possible burnout? since certain android build factory resets still saves some data on there if someone were to make an app for it.