Start with a moment someone can describe
Choose a specific moment: reviewing feedback after a training session, or receiving a task and confirming it on site. Turn broad goals such as wellbeing or productivity into an action a person can actually complete.
You do not need a complete feature list yet. Understand how the task happens today, where it becomes awkward and why a device worn on the body might help.
Put the first-version decisions on one page
A first brief can cover five things: the user, the main task, the wearing and working environment, essential functions and functions deliberately left for later. Add how the device relates to a phone or an existing business system.
Every essential feature needs a reason. If removing it leaves the core task intact, it may belong in a later discussion. More features also introduce more questions to test.
Choose the information before choosing a screen
Frequently reading tasks and checking values is a different interaction problem from receiving a simple reminder. Establish what must appear on the wrist, how long someone can look at it and whether their other hand is free. Then consider a small screen, no screen, buttons or another approach.
Connectivity, battery life and physical design need to be discussed together. Selecting them in isolation can leave difficult compromises for the assembly stage.
Give the prototype a question to answer
The first prototype may have a narrow purpose: test wearing comfort, readability or an end-to-end data connection. Write down the question and what evidence would answer it.
Product definition is not a promise to resolve the entire future in one meeting. It is a shared decision about the next useful step. A one-page brief often makes that decision easier than a long, unprioritised feature list.
