We should instead question whether we need the information that is being communicated in the first place, because even a colored LED or a soft haptic buzz can be stressful when we know what they mean. Maybe we should minimize the use of such technology instead.
In my view, calm technology only functions when you use it. It answers your questions or solves your problems only when prompted to do so. Maybe a robot vacuum cleaner that beeps on faults and vacuums on its own initiative is helpful technology, but with alternatives that won’t have any reasons to steal your attention I can’t say that it’s calm technology. IM with a soft haptic buzz to notify you of the receipt of a message may again be immensely helpful, but an email account that I check myself when I feel like reading messages is more calm.
If your life seems calmer when you know exactly when you’ve received a message regardless of what you are doing at the time or the nature of its content, you should perhaps think of how to lead a calm life before worrying about whether a pleasant beep or a soft buzz is the best way to direct your attention to it.
This is why I love Apple for pretty much eliminating blinking lights in their devices, while other manufactures of laptops etc. still don't seem to get it.
The only lights remaining in my room at bedtime are the power strip and external hard disks, and even they can be annoying.