Get the chargin process intensity I link my Samsung Galaxy S3 to the computer's USB port using a non-original power cord. 
I've found charging process very slow, so I would test the intensity whereby power cord supply  energy to the phone.

There's an app for this?
Use "Battery Monitor Widget" app from Play Store. It can monitor the current flowing through the battery while charging. 
I identified my Nexus 7s charger and an aftermarket charger's performance this way.