What you are describing is do-able, and in fact has been done before, many times. It sounds like you are re-inventing Nagios.

You might want to check out the Nagios site and see if there are already plug-ins that will do what you want in the way of Oracle monitoring. Worst case, you will find that your exact probe doesn't exist; but you can easily modify one of the existing probes to fit. Nagios provides the framework to do most, if not all, of the heavy-lifting for you, so you only have to write and debug a few lines of code to implement the probe.

It's usually better to go with an already developed tool that has been battle-hardened than write your own and go through the pain of (re)discovering all of the edge-cases and pointy-bits that hurt.

Update -- Corrected some misspoillings