Still very happy with the GPS solution, still sticking to the original GPS receiver. The XAiOX iTrackU did work as well, but did not provide the advantages I was hoping for. I thought I will be notified when the battery is low and yes, it does. With a loud and scratching voice. You can turn down the volume but just in three steps and it is still very loud. So I returned it.
For the summer holidays at the windy beach of
Fuerteventura I installed a 18mm O-ring seal you can get at any DiY shop. The Mini-USB connector I sealed with an adhesive tape, on the image you see a white one.
In the first image you see the bluetooth adapter mounted...

Second image shows the backside of the adapter with the O-ring seal...

And from a different perspective