I needed a way to start an application when a device is connected to the RPi. In this example the barcodescanner software should start when we connect the scanner. Adding a udev rule should do the trick.

• First get the ID of the specific device

lsusb

    Bus 001 Device 006: ID 05f9:2214 PSC Scanning, Inc. 
    Bus 001 Device 004: ID 0a5f:0015 Zebra

• Add the rules file located in /etc/udev/rules.d/, for instance /etc/udev/rules.d/85-custom_usb_device_rules.rules

• Add the rule to detect scanner and start software, the idVendor and idProduct point to the ID we got from lsusb

ACTION=="add",SUBSYSTEM=="usb",ATTR{idVendor}=="05f9",
    ATTR{idProduct}=="2214",RUN+="/etc/init.d/barcodescanner start"

• Reload the rules or reboot

udevadm control --reload-rules

List of ID’s