Zenviron app provides real time PM2.5 data from the closest functioning EPA/AirNow monitor. The first screen shows the PM2.5 data at users current city. Users can also search for other cities.
The app shows historical information as provided by EPA/AirNow as well. The last 7 hours data in a day and the last 7 days data is shown.
The color coding is as per the EPA standards provided here.
http://airnow.gov/index.cfm?action=aqibasics.aqi
This app is optimized for iPhone 6 portrait layout.