Do I need Zigmo if I am using a Mega Modem?

I have not purchased Zigmo yet, as I was under the impression that I could use the Mega Modem and the acceleration impact detection sensor without it, but setup is proving to be difficult since there are many references to needing the Zigmo. Can I use the Mega Modem in its place?

yes, you can use MEga modem as zigmo as well.
It also mounts as a USB-Serial device and you can use labview and Alpha station to read the sensor and to make changes.