Small devices on a boat
The options for electronic navigational assistance on a small boat divide into two broad categories. 1. Dedicated chart plotters from well known marine manufacturers 2. Apps running on small computers (laptops, smart phones or tablets).
Disadvantages of the first category include expense, and inability to run third party software. On the other hand there is a very large range of available navigational software for the second category, though quality does vary.
One advantage of using small computers is that it is easy and relatively cheap to add redundancy (and therefore safety) by obtaining additional devices. Most sailors already have a laptop and a phone, so by adding an additional tablet, its possible to have two levels of backup