I lost my Apple Pencil yesterday when some kids were using it (I didnt realize it was lost until last night). By opening the iPad Pro and looking at notifications to see the battery levels for the iPad and pencil, that wakes the Pencil up. Then I used this app to look for the strongest signal (-30 dBm) in this case. The app actually identified the Apple Pencil after about ten minutes. Then I dug down into the couch at that point - and there it was! Thanks for saving me lots of money!
RG Fleck about Bluetooth Smart Scanner, v1.0.7