It would be great if we had the possibility to show a ruler around the map. This ruler should change as the projection change as well, and the frequency of the ticks should be configurable as well (eg. show the latitude every 10km and longitude every 5km if we are dealing with an UTM projection or latitude every 2º and longitude every 3º if we are dealing with geographic projection). It should be something like that:

Another example:

We already have a scale bar, which is great, but it would be very good to be able to see the ruler around the map.