The Tension Labs EAP03 Earphone Audio Processor seems like a good idea.  It has a microphone that you can set to allow some outside noise into earphones that isolate you.  It can show just how many dB you are inflicting on your eardrums and incorporates an equalizer.  Unfortunately, when TechPowerUp tried it out it lacked the power to stand out among the crowd.
“Tension Labs EAP03 is the name of a brand new earphone audio processor that can boost your experience in a variety of ways. The EAP03 features a built in microphone and can sample it into the audio feed, providing you with the power to control the level of isolation you want from your earphones.”

Here is some more Tech News from around the web:

Audio Corner