The Scouting app is a mobile device Scoutbook app that can be used by Scouts and parents whose units use Scoutbook.  After the parent has been connected to their Scout in Scoutbook, they can log into the app with the same userID and password they use for Scoutbook.  To find it search for Scouting BSA in Google Play or iTunes Also see the article here

The MyScouting App allows for access to myScouting from your mobile device (e.g., phone)
To find it search for myscouting in Google Play or iTunes

There are no specific apps for leaders to access Scoutbook or Internet Advancement. Leaders simply open a browser on their phone and go to http://scoutbook.com or
https://scoutbook.scouting.org The tools are smart enough to auto format for your phone.