Is is possible to install an aftermarket GPS in my Prius II?

Infael

2004 Gray Prius with smart start/entry and VSC

In-dash, through MFD? No. Toyota makes no offer and I can only assume it is because of the complexity of trying to modify an existing vehicle with their implementation of that system.

I highly recommend the Garmin Quest. There are certain advantages it has over other systems because of its portability and the price is hard to beat. About $500, which is really good for what it does and what you get.

It has been said:
Hybrid drivers come in 3 flavors, greenie, techie and cheapie. Pick any 2.
2005 Prius, Melinium Silver over gray, package 5 (AI)

you can... with coastal e tech's viewtech but you have to buy the viewtech that hooks up to the screen as well as the aftermarket nav separately

A Prius a day keeps the doctor away!