Nokia's long-rumored Treasure Tag smartphone accessory is scheduled to arrive in April. The $30 gadget is designed to connect to your car keys, purse, backpack or any other valuable that you wish to track via a combination of Bluetooth and NFC. Here's how it works.

To pair, simply connect using NFC or search for it with Bluetooth on your Lumia smartphone. Once paired, users will be prompted to download the Tag app. From here, attach it to something you wish to keep track of.

For example, let's say you've attached the tag to your backpack. Perhaps you're late for class one morning and rush out without grabbing your bag. Your Lumia phone will emit a loud tone to alert you that you've forgot the bag. Conversely, if you leave your phone behind and rush out with just the backpack, the tag will also produce a similar tone so you know to go back and grab your handset.

Should you leave your bag at home on purpose (say, during the weekend), a simple long press will deactivate the tag. Alternately, you can mute the alarm on the phone or put it into sleep mode within the tag app.

The accessory, available in cyan, yellow, white and black, measures just 30 x 30 x 10mm (about the size of a match box) and weighs 13g. We're told the tag's internal battery will last around six months and fortunately, it can be replaced once it goes dead. Up to four different tags can be connected to a single phone at any given time, Nokia says.

Nokia Treasure Tags will initially only be compatible with Lumia phones but there will be third-party apps for tag support in Android and iOS.