Welcome to the forum.
Yes - I have the BTM03.
I was rather dismayed that the XT didn't have a wired connection. The 590 has a bunch of wires and they have been trustworthy and hassle free. My few excursions into BT connections have not been as successful. So I was not best pleased at being forced in that direction.
But the BTM03 is working very well. I have had a few glitches, but these rarely happen now that I have got it settled in.
First big problem was the qaulity of the sound. I wrote to Chains peed about it, and asked if they had come across the badly tuned in radio station symptoms that I was experiencing. They hadn't. But I had one more test to try. I had put the module in the rear of the bike where my autocom unit is and also away from the ignition. Unfortunately, that is where the Engine's control unit is on my bike. So there was some delay while I got a 4 pole male to female 3.5mm extension lead to connect the BTM03 to the Autocom.
You have to read the autocom instructions about plugging into the 4 pole sockets. One of them provides a power feed, and if you plug it into that, something will blow. I can't remember which one mine is plugged into - but I taped over the powered 3.5mm socket so that I didn't make that mistake.
The BTM03 is now located in the fairing (I have a Pan European / ST1300), so it is under the nose, above the headlight. I've got that on the right hand side, and my satnav is on the left. I have this idea that radio signals (like BT) are best if the sending device and receiving device are not next to each other. I don't know if that is a fact, but I must have read it somewhere. Whatever, they can only be about 18inches apart and it works fine.
The next issue was that the signal between the BTM03 and the XT kept being dropped.
There were a number of reasons for this:
1) The phone, and the XT both have a bank of devices that they will connect to automatically given half a chance. When setting off from home they can end up connecting to the wrong devices if they are switched on in the house. Later when they try to connect to each other, the BT Module sometimes gets dropped.
2) The XT and phone can go off hunting for other BT connections if they are allowed to. When passing cars, they too have BT devices that hunt for nearby phones. So at apparently at random, the BTM03 will drop - but I discovered that it never did it on quiet roads with no traffic. So I suspect, but haven't proved, that that is what it was doing.
3) I have noticed that sometimes if I after turning on the ignition - which powers the XT and the BT module, I need to remove the key to open the top box - that truning off the power and then turning back on again causes problems. I think that has to do with the fact that the XT doesn't turn off immediately, so it notices that the BTM03 isn't there and starts making other connections.
I have now got into the habit of disabling my home based BT devices from my phone and my XT before I set off so that the phone can only connect to the XT and the BTM03 can only connect to the XT.
If there are problems with the sound connection, then I turn off the BT connection on the XT and then turn it on again. It relinks to the phone and BTM03 quite quickly and all is well again. Only occasionally when this didn't work, I had to forget the BTM03 device on the XT and make the XT search for it again.
Then there is the volume problem. I had been stopping and starting trying to sort out the issue - why were the autocom instruction so quiet. I could hear them but nowhere near loud enough and only if i was going slowly. It took a few incidents like this before I realised that it was the same problem. The XT hadn't connected to the BTM03 properly so all of its sound output was coming through the XT speakers - which is why I could hear it but only quietly !
There is one issue that I have not solved. That is playing music from Spotify on the phone through to the XT. I rarely want to do this - cos there is very little control of Spotify from the XT, and I rarely listen to music anyway. It affects my concentration. But the music would start pausing occasionally - for half a second or so. Then as time went on, the pauses would become more frequent. Then it would be unlistenable.
I couldn't pin it down to the Zumo, the BTM03 or the phone although I tried everything that I could think of. It seemed to be the combination of all three things together. I gave up with that. If I want music I put mp3 files on the XT and play those. There is much more control too.
All of this paints a pretty grim picture. But it isn't. Once it is all sorted the BTM03 works really well. The sound is crisp and clear and in stereo. It works well with phone calls on the move. I 've written all this stuff because when I bought the unit, there was no one to help me - we had got into the first Lockdown and last year, and no one was available to take the calls. Most of the time, now I have a procedure, it works extremely well.
Occasionally I do still get a glitch, but this has only happened when I have forgotten to unpair other stuff, or when I have turned on the ignition and then turned it off again.
And the fix if necessary is always simple. Turn off the XT BT on the screen. Wait a couple of seconds and turn it on again. Wait until all of the icons go blue. Like this.
Today, I discovered something really important. I found another way that doesn't work.