There is an app called former Geooh Live and will soon get re online as Geooh Go, there the message center is implemented and works. It is similar to the original geocaching app.

This app is right now in pre beta phase and I am in this beta too. Maybe I can show you how this is implemented.

Maybe new caches that was loaded from livemap you can display in another color. So you can see directly what is new.

Looks nice, but maybe we don't need a difference, but it is a good idea the different colors.

For example in Locus all databases could be shown, but you can mark the databases that should shown. There is no difference in optik. But this could be a good idea in GCDroid.

In CacheSense (retired) there was this option to, to color different databases on the map.

I like this idea. 

In a view other apps like C:geo, Locus, Cachebox, CacheSense (retired) this was implemented and works great. Standart there was the offline map and the only is started when clicking on a button. Then you have both, offline and live view.

I think there was an extra database for the livemap, that was shown, when active.