This app was mentioned in 1 comment, with an average of 1.00 upvote
Glasgow Bus Finder app is great. Says 'Glasgow' but seems to cover most of the surrounding areas. Definitely works for Paisley/Renfrewshire local buses as well. Think it pulls the data from Traveline's database.
(https://play.google.com/store/apps/details?id=teamk.glasgowbusfinder)