Some observation on the simple logger after a few days of testing: (FW V3000)
I found the device is quite easy to use and learn to setup and connect.
It has one button and one LED. The back has slots to thread the arm band through.
Of course, the simple logger does not have a screen and cannot provide any feedback on the water.
The download of files to Windows, Macintosh and Linux computers is straightforward via WiFi connection to your computer or some smart phones using a Browser, although I found it can take a while, up to a minute or more to make the WiFi connection and do the download. It can also take 30 second to a minute to go to the next menu page. Have patience, it will happen if you wait a bit.
The device also has some nice built in browser tools for naming and organising you session data.
Updating of firmware also looks quite straightforward through the same interface.
There are very few options in the settings. It is set to log at a fixed 10Hz. The user can set the username, speed and distance units and the Time Zone.
The logger saves the data in the .OAO file format like the LCD screen Motion. This can be read directly by all the popular analysis programs, but not by RealSpeed without conversion.
The device is set to use up to 20 of the best satellite signal sources from three GNSS systems, GPS, GLONASS and Galileo. (Apparently, this has been adjusted to 18 bests in FW V 3001)
I have not tested ultimate battery endurance.
Waterproofing seems bombproof. It is completely sealed (potted) in plastic.
It comes with a simple elastic strap for wearing on the upper arm. This may be problematic for a couple of reasons. It can slip aound and under the arm too easily. It could also be stripped completely off the arm in a crash and be lost as it will not float. I recommend using it in one of the common arm band bags to that even if it stripped off in a crash, it should still float and be easily retrieved.
It is quite small compared with all other devices. It is approximately 50mm x 54mm x 13.5mm. It will most likely easily fit inside many helmets.
The induction pad for charging that is included with the GPS and seems to work well
The Motion simple logger, like all other such devices, should be worn on the upper arm or head for best results. because it is, by design, setup to only use satelltes with a strong signal, it does not work like some other GPS when worn in a compromised position in that it may quickly drop to using a small number of satellites if sky view is compromised. This means that it may not record data or might have lost points if worn in a pocket on the front or back of the body, and beneath any material that can get wet and therefore reduce satellite signal strength. See Juliens logic and description in an earlier post - this may sound like a problem to some people, but it is actually a very well thought out advantage.
A picture for size comparison: