According to Apple’s release notes, macOS Monterey 12.2.1 addresses a bug that was causing Bluetooth devices connected to Macs to drain an excessive amount of battery. You can download the update by doing to System Preferences —> Software Update
According to Apple’s release notes, iOS 15.3.1 and iPadOS 15.3.1 fix an issue that could cause Braille displays to stop responding. It also “provides important security updates.” You can update your iPhone and iPad by going to Settings —> General —> Software Update.
watchOS 8.4.2 is a maintenance upgrade with bug fixes and security updates. It can be downloaded for free through the dedicated Apple Watch app on the iPhone by going to General —> Software Update. To install the new software, the Apple Watch needs to have at least 50% battery, it needs to be placed on a charger, and it needs to be in range of the iPhone.