Choose a timer you can hear and stop
The best tea timer is the one that fits the room, your hearing and the way you make a cup.

Decide where the reminder needs to reach
A quiet chime may be pleasant beside a desk and disappear completely under the extractor fan. Before choosing a timer, think about where you stand while tea steeps. If you leave the kitchen, a visual countdown on the worktop will not be much help. If other people are sleeping, a piercing alarm can be equally unsuitable. Adjustable sound, a clear display or a wearable vibrating reminder may matter more than a long list of programmes. Check the actual features of the device rather than assuming every digital timer includes them. The useful question is whether the reminder will reach you without making the household work around it.
Try the controls before relying on them
Set the time you normally use, start the countdown, stop it and reset it. On some timers that takes a few direct presses; on others you hold a button while the digits scroll. Neither approach is automatically wrong, but an awkward sequence becomes tiresome when repeated every morning. Look for buttons you can distinguish easily and a display readable from your normal position. A device with several channels is only useful if you can tell which alarm belongs to which job. If tea and dinner are timed together, use clear labels or separate reminders rather than trusting yourself to remember a row of similar numbers.
Match the reminder to the action
Choose a consistent moment to start timing, such as when you begin pouring, and keep that convention while comparing cups. Have somewhere ready for the wet infuser, because hearing an alarm does not stop extraction. Remove the leaves or decant the tea when the reminder sounds. A phone timer can do this perfectly well if you can hear it, access it easily and avoid confusing it with another alert. A separate kitchen timer is useful when you would rather leave the phone elsewhere. There is no need to buy one solely because it is sold for tea. After a few days, judge the setup by missed reminders and easy repeat use, not by how impressive its display looks on the counter.