There are subtle differences. All suggestions are grammatically valid, but the context may invalidate some of them.
"The data supplied by a Myo sensor [...]"
My thoughts on this are, that the first is definitely incorrect, because the Myo itself is not a sensor.
Your reasoning is invalid. A car door is "the door of a car", it does not imply that "a car is a door".
Similarly, a Myo sensor is "the sensor of a Myo".
The data supplied by a Myo sensor [...]
This is correct, as long as your statement applies to all the sensors that are found on every Myo. It is a universal statement.
Note: pedantically, this implies that Myo sensors all (individually) supply data. This distinction is very minute, so it may be overly pedantic for your current case. But I thought it'd be interesting to point it out.
"The data supplied by a Myo's sensors [...]"
Here, "a Myo's sensors" means "the sensors of a Myo [product]".
This is correct, provided that it is correct to call the armband "a Myo". I would assume that that is indeed the case.
Note: pedantically, this implies that there is combined data that is supplied by the sensors (as a group). This distinction is very minute, so it may be overly pedantic for your current case. But I thought it'd be interesting to point it out.
"The data supplied by Myo's sensors [...]"
The absence of the article implies that you are talking about the company (presumably called Myo), not the product (presumably also called Myo).
Consider this example:
A Mercedes' car doors are always high in quality.
Mercedes' car doors are always high in quality.
The first refers to the car, the second refers to the company.
This is grammatically correct, as long as your statement applies to all the sensors that are produced by the Myo company.
However, from context, I gather that you are focusing on the armband, not the company, and therefore I consider this suggestion incorrect (for your current context)
The second is missing the article, now I am pretty sure that I have to use an article, as a Myo is nothing unique,
You're right that the use of an article changes the meaning (from the Myo product to the Myo company).
there are multiple existing Myos and I have to specify whether I mean any Myo or a specific one by use of an article.
You're correct when you say that using the article makes it clear that you're referring to a product directly. However, if there are many products (or types of product) called Myo, then "a Myo" does not help with disambiguating which of the products you're referring to.
"a Myo" still describes all possible products named Myo. However, it's possible that your context has already made it clear which type you're focusing on.
e.g. if this is found in a document which explains how to use a particular type of Myo, then it's contextually obvious that you're focusing on this particular type of Myo.
People don't say: "People use a human's legs to walk.", they say: "People use human legs to walk".
Their examples are correct, but their reasoning is flawed and their example is contrived. No one says "People use human legs", because you can omit the "human" without changing the meaning: "People use legs".
"People" already inherently means you're talking about humans. However, the same is not true for "The data supplied by a Myo's sensors", because "data" does not inherently mean you're talking about Myo or sensors.
Their argument for not using the possessive is flawed. They seem to be arguing that one is correct and the other is incorrect, but that it not the case. Both are correct, but they have different meanings.
Consider the following examples:
- This Mercedes has a BMW engine.
In other words, the engine is made by BMW (the company).
- This Mercedes has a BMW's engine.
Comparatively, this example states that the engine was taken from a BMW car.
In most cases, these can be used interchangeably, but not always:
- If the engine was made by BMW but never put into a car (before it was put into the Mercedes), then only example 1 is correct.
- If the engine was built by another company (e.g. Volkswagen), placed into a BMW, and then placed into a Mercedes, then only example 2 is correct.