Since the version 3.2.0, Locus Map offers full access to user's field notes. For this access a system called Content provider is used. You don't have to be too skilled with it. Most of required work is already done in Locus API and you may (and it's suggested) use already pre-prepared functions.
To access field notes in read or write mode, you need
For read only access
<uses-permission android:name=“com.asamm.locus.permission.READ_GEOCACHING_DATA” />
For read/write access
<uses-permission android:name=“com.asamm.locus.permission.WRITE_GEOCACHING_DATA” />
Field notes in Locus are stored in SQLite databases, so all queries sent over Locus API to content provider may be defined in probably well known way for you - same as a query to SQLite database.
What is possible
To use basic features check FieldNotesHelper.java class.
Here are three very important parts: