Hi Vedanth,
In my point of view , you can achieve this in standard SAP itself by using inventory transfer menu.
Create a warehouse in the name of vendor name and post the inventory transfer documents when you send a items for servicing , here give your newly created warehouse in TO warehouse field . Again create a inventory transfer when your items return back from your vendor.
Note: If need only Add-on means , Kindly post your add-on issue in the below link
