Kaktus Circuits created this board to analyze USB devices:

Tindie Blog: USBuddy

Easily tap into the USB signals coming and going while the device is still connected to the bus [..] monitors power consumption [..] handy for reverse engineering devices without having to take the device apart

The assembled board can be purchased on Tindie.  The hardware design files have be shared on GitHub:

 kaktus85/USBuddy