Officially Oracle Golden gate can be monitored in 3 ways:

1. Oracle GoldenGate monitor (Requires a database as repository: Oracle, MySQL or others)
2. Oracle Director (I guess the same as 1) )
3. Scripts (for people without money, like me :) )
4. Integration with Nagios

So let's get going. Firstly I will start with the scripts, since it is the cheapest (7 hours to deal with the Google SMPT Server and 1 hour for the script.