Buster (iOS)
Used by 2 peopleapps.apple.com ↗

“And for real-time, GPS-based tracking of exactly how broken the CTA is, there's Buster.”
Nick Disabato Interview, Designer, tree killer (Distance, Cadence & Slang) · via Uses This 
“iPhone apps I use daily: Buster (real-time Chicago bus tracking).”
Adrian Holovaty Interview, Web developer (EveryBlock, Django), musician · via Uses This