The Polar M400 is a GPS watch with a built-in activity monitor, which means that in addition to your training it also tracks your daily activity in steps, calories burned and even how you sleep. The M400 is the second Polar watch to feature an activity monitor after the V800. And if we have Polar Loop, it would be the third device from the brand that monitors activity. So I guess Finns know what they're doing after so much experience.
The M400 is primarily intended as a running watch, but it also offers a number of sports profiles, including cycling and swimming, but it is not a triathlon watch at all. You can think of it as the little brother of the Polar V800 (which you can read the review of here). Or the poor brother. And you can look at this in two different ways:
It is a "low cost" watch that has had its features removed and the quality of its materials reduced in order to lower its cost and make it more competitively priced.
You won't pay for features you don't use or need. You don't swim, so you don't need specific swimming functions or underwater pulse recording. Your cycling is non-existent or testimonial, so you don't care if it doesn't support sensors. Your races are relatively short and you don't need more autonomy than the 8 hours it offers. You don't go ultras or run in the mountains, and you don't need navigation either. In other words, if your profile is that of a pure asphalt runner, this watch is much more adapted to you.
In short, both assumptions are correct, because this is a Polar V800 "cut", both in performance and in materials used. But if you are not going to use these features, why do you want them? And, above all, why are you going to pay for them? Not having these features does not make it a bad watch, but a watch more adapted to a less demanding customer.
There is only one feature of the Polar V800 that is missing, and that is the lack of vibration warnings. The Polar M400 only has warnings by beep. The problem is that the volume of those warnings is quite "modest", so if you run in noisy environments it is easy that you do not know. But you still have a watch with Bluetooth connectivity and also microUSB (you can charge it with any charger), waterproof up to 30 meters, with a very good resolution and illumination screen and customizable views with up to four parameters, with some Smart Coaching functions, etc.
The best thing about this watch is, without a doubt, its price. 160 euros without a pulse sensor and 200 euros if you want to get the pack that incorporates the Polar H7 (which also has a 5 kHz band for swimming, but which the M400 is not capable of receiving). This is a fairly competent rival to other watches in the same range, such as the Garmin 220, which is about 50 euros more expensive right now (and without support for other sports, although with vibration).
The trial period has already begun, and I'll bring you the full analysis in the next few weeks. In the meantime, you can entertain yourself by taking a look at the Polar M400 image gallery.