Yes, as mentioned, there are many mounts available for iPads, even marine specific ones with fully waterproof cases. There are apps for iPads and iPhones that are meant specifically for navigation. Companies like Navionics, Garmin, and others make mapping/charting software that cover the globe, and along with the very good processing of an iPad, are very good, reliable chartplotters. Ipads are used in many boats and megayachts, even some ships have them as backup and redundancy.
For those that aren't aware, even Bizer has a dedicated app for navigation using an iPad.
The 3G/4G models have integrated GPS however, being somewhat marine savy and experienced myself, I am naturally apprehensive about trusting my position to the inferior GPS receiver built in to the iPad. This is why I'm interested in an external GPS antennae, and especially interested in one with GLONASS capabilities.
I believe this may be a relatively new antennae so maybe not too many people own them yet, I suppose I might be one of the first.
I'm hoping one of you have tried this out and have an opinion on it.
Basically, GLONASS just refers to the Russian GPS satellite's that we now have access to, so in essence, it gives us the ability to use an additional 24 satellites for GPS navigation. It's more reliable and more accurate.