Tech4o is what Silva use as a general brand for all their watches. Mine is Traileader 1. I have one on Test at the moment with BGT. I can't find EchoMaster on the www.silvacompass.com web site.
I have found that the altimeter is stable enough that I don't recalibrate the watch at all. Yes, the apparent altitude will go up and down with the weather, but if I leave it strictly alone and don't fiddle with it, it always returns my house to the same altitude once the front has passed.
So, what I do is to note current deviation when possible and remember that. Eg: storm coming, pressure drops, altitude reads maybe 20 m high - I memorise that correction.
Recalibration - well, there are TWO factors here. One is to correct the 'zero' on the barometer. If your watch on your wrist persistently reads +20 m when you are on the beach on a fine day, you might want to adjust that back to +1 m. Fair enough. But only do it once.
The other parameter is the relationship between barometric pressure and altitude. I THINK, but I may be wrong, that you can tweak this as well, but the manual strongly recommends you don't. I haven't even considered touching this.
HighGear: I Tested an Axis watch with BGT. You can read my reports there. The first watch the company sent could not calibrate the compass at all: it was faulty. The second one could 'calibrate', but after I did an extensive calibration test on the compass function and sent the results to Highgear, the company withdrew all the Axis watches from the market. Yeah, I'm serious! It was that bad!
The Axis was redesigned and a new version released. The displays were different, and so were the insides. The new one was better but the compass was still unusable imho. Unfortunately, the battery replacement arrangements proved to be impossible: I simply could not get a new battery into the watch such that the watch worked. Trust me, I tried!
I am currently using both the Tech4o TraiLeader and the 2nd Axis unit. I just don't even look at the compass function. The Axis is smaller and lighter than the Tech4o unit, but the bug-ridden software correction system the Axis has for variations in the weather makes the altimeter very unreliable. It isn't hard for the altitude of my house to rise over a couple of weeks by 100 m.
The problems with the Tech4o are the huge physical size of the watch and the very cumbersome strap on it. The watch is really aimed at the young psuedo-outdoors male machismo market imho. Apart from that it works very well for time and altitude.