Why can’t my Garmin GPS unit triangulate the position of a landmark for me? It’s got a built-in compass, and it’s got sight-markings on the casing for point-and-go navigation (you have to estimate the distance to the landmark).
It would be great to be able to say ‘I can see it now if I look in this direction’, and later in a different place say ‘I can see it from here too, but in that direction’, and have it put a waypoint on the map for me estimating the position.