If you're looking for a small and genuinely useful Christmas gift for someone this year, I can personally recommend Apple's AirTag item-tracking devices. They're great for anyone who has an iPhone, but particularly with iPhone 11, iPhone 12 or iPhone 13 models, because then if you lose your keys (or whatever they're attached to), your iPhone can literally point you towards them with a big arrow.
An individual AirTag costs £29/$29/AU$45, or you can get a pack of four for £99//$99/AU$149. If you order from Apple directly, you can get them engraved with a couple of letters or an emoji symbol on the front, too.
Each AirTag is just a simple little disc, white on one side and shining metal on the other. You can get keyring holders, luggage tags and other accessories to make it possible to attach them to whatever you need, though you can always just slip one into a purse or handbag pocket as is.
To set them up, you just hold one near your iPhone, and then a screen will pop up on the phone and guide you through the short and sweet process. After that, if you need to locate an AirTag inside your house, you can just use the Find My app to have the AirTag make a noise, or even to point you in its direction, if you have one of the newer iPhones mentioned above. With an older phone, you can still have the AirTag make a noise, and the app will still tell you that the AirTag is within a matter of feet of you, you just won't be able to see which direction it's in.
And if you realise that the AirTag isn't at home, and you've lost the keys somewhere outdoors, the Find My app will tell you where you last had them, and can tell you where they are more recently, thanks to the Find My network.
AirTags use Bluetooth to always broadcast their position to any iPhones within range. If that iPhone is yours, then it'll tell you that the AirTag is nearby. If that iPhone is someone else's and you're nowhere nearby, it'll piggyback that iPhone's internet connection to tell you roughly where it is (using encryption to make sure only you can see that information) – that's the Find My network in action. And since iPhones are so popular, unless you lost your keys in the middle of the jungle, odds are someone with a suitable phone will be walking past before too long.
Really, the gift you're giving here is a bit of peace of mind. That when you're rushing in the morning, it'll always be easy to locate your keys; or to know that your luggage is somewhere on the carousel even if you haven't seen it yet; or to be able to find your bike in a big and busy bike park.
(And for those concerned about how AirTags' tracking ability might be misused, Apple has a page detailing how an AirTag will alert a person if its found to travel with them a lot but doesn't belong to them, and what do in that case.)
The only disappointment about AirTags is that they're for iPhone only. For Samsung phone owners, we can recommend the Samsung Galaxy SmartTag Plus tracker instead, or for something that works on iPhone or Android, the Tile Mate is an ideal replacement.