Using HRM4 without watch

Will this setup work or is the watch required?

The HRM4 chest strap will broadcast the user's data over ANT+, irrespective of whether there are any devices in the vicinity listening.

Your mobile handset is capable of receiving the broadcast. I don't use Strava (and I'm not about to look into it by consulting the same documentation you would also have access to), but I know from first-hand experience that the Wahoo Fitness app on Android running on my Samsung Galaxy S5‑Mini can read and use the data broadcast by my HRM4-Run.

In addition to the HR, I'm hoping that the HRM4 will also add the running dynamics data - I understand that I may need to install a Garmin app to view some of the running dynamics data

The ability to interpret the Running Dynamics data (which is sent using Garmin's proprietary format) rests with the compatible wearable device (FR630, FR735XT, FR935, fēnix‑5, etc.) and not the app. Even if you were a Garmin customer with an HRM4-Run chest strap and a FR230/235, you still would not be entitled (or able) to access the Running Dynamics data.

I hope that clears things up for you.

Thanks ASmugDill.

That's good news from the perspective that I can purchase the HRM4 and benefit from HR data now. In order to get the extra data I'll need to wait until I get the watch :)

Even if you were a Garmin customer with an HRM4-Run chest strap and a FR230/235, you still would not be entitled (or able) to access the Running Dynamics data.

I hope that clears things up for you.

Are you saying that the HRM4-Run is not using the standard ANT+ HR Running Dynamics profile? It certainly looks like it is to me (the HRM-Tri as I don't have a run, but the RD is the same I believe?)

Of course I don't know of any ANT+ android software that supports RD but the profile is standard and you most certainly are entitled and easily able to access it once you get ANT+.

Are you saying that the HRM4-Run is not using the standard ANT+ HR Running Dynamics profile?

I cannot access www.thisisant.com right now (because its web server appears not to be available), but there was no ANT+ Running Dynamics profile until recently. The excerpt from the Google Search match states, in the first two lines,

The ANT+ RD device profile will make its first appearance in Garmin's new Running Dynamics Pod, which releases alongside the new Forerunner 935.

so you cannot reasonably expect earlier Running Dynamics-compatible chest strap to be using an ANT+ profile that didn't exist.

It certainly looks like it is to me (the HRM-Tri as I don't have a run, but the RD is the same I believe?)

OK then, from what exactly does it “look like it”? Care to point us to authoritative references and/or product specifications, instead of just extrapolating out of wishing thinking from something new on the market

Are you saying that the HRM4-Run is not using the standard ANT+ HR Running Dynamics profile?

It is not.

It certainly looks like it is to me (the HRM-Tri as I don't have a run, but the RD is the same I believe?)

The HRM-Tri uses the same ANT+ profile as the HRM-Run for running dynamics, but it is not the ANT+ Running Dynamics Profile.

Of course I don't know of any ANT+ android software that supports RD but the profile is standard and you most certainly are entitled and easily able to access it once you get ANT+.

The thing is that the RD ANT+ profile is very recent. All Garmin running dynamics devices - except the quite new RD pod - use a proprietary ANT+ channel for RD. In theory this might change with a firmware update.

so you cannot reasonably expect earlier Running Dynamics-compatible chest strap to be using an ANT+ profile that didn't exist.

The HR-RD profile is the one used by combined HR running dynamics devices such as the HRM TRI / HRM RUN - which was ratified at the same time, the proposal was just a ratification of the Garmin implementation as I understood it.

OK then, from what exactly does it “look like it”? Care to point us to authoritative references and/or product specifications, instead of just extrapolating out of wishing thinking from something new on the market

The ANT+ messages, there's no wishful thinking, but I've not fully checked the messages fully meet the standard, that would take a lot more effort than simply looking at the ANT+ message as they go by. And you are certainly entitled to access it, and are trivially able to access it (simply record all the ANT+ messages!) it appears to meet the standard too. If garmin want to appear on their forums and state that the HRM4 is not compatible with the ANT+ HR RD profile then I'm sure they can, I would really encourage no-one to buy it if they did and wait for a device that is compatible to standards. I'm pretty sure it is compatible though.

The HR-RD profile is the one used by combined HR running dynamics devices such as the HRM TRI / HRM RUN - which was ratified at the same time, the proposal was just a ratification of the Garmin implementation as I understood it.

I tried to delve into the topic and it looks that you're right. A notable excerpt from the DC Rainmaker article:

Now there is one more minor technical nuance that’s interesting here. See there are actually two new devices profiles: RD Profile and HR-RD Profile. The RD profile is used for standalone products like Garmin’s RD Pod, or potentially something like Stryd’s newish running pod. Whereas the HR-RD profile (Heart Rate-Running Dynamics) would be used for products like Garmin’s HRM-TRI/HRM-RUN heart rate straps that combines heart rate data with running dynamics data (and the same with Stryd’s Gen1 HR strap product).

So which devices support this today? Well, that’s where it gets a wee bit tricky. Right now it’s the Garmin Fenix 5, Garmin FR935, Garmin FR735XT, and Fenix Chronos for the vanilla RD Profile (which is what the Garmin RD pod uses).

However, the HR-RD profile is *exactly* the same as the existing/previous Garmin Running Dynamics spec. That means that if Wahoo or whomever were to implement the HR-RD profile correctly in the TICKR for example, it should actually work with *any* existing Garmin Running Dynamics capable units. That would be: Garmin Forerunner 620, FR630, Fenix 2, Fenix 3/3HR, FR920XT, FR735XT, FR935, Fenix5/5X/5S.

So my conclusion is - if I understand correctly - that the RD profile is not backwards compatible and available only on latest devices, but the HR-RD profile is backwards compatible with existing Garmin RD devices like the HRM-Run or the HRM-Tri.