Hi All
This is something I have thought about a lot - for a Long time - I am thinking about changing to an IS and would like to install something like this. One of the big issues to me is that I would retain a stock look - That is the big appeal of THESE aftermarket systems
When I was looking around for aftermarket systems I came across this one
https://www.ebay.ie/itm/182655430616?ul_noapp=true
It APPEARS as though this MIGHT be the one for cars that do not have SatNAv originally installed
However, there is another way to go about it and that is to build your own system. There are at least 2 books about that - One is called "Car PC hacks" by Damian Stolarz. This was published back in 2009 and is Very detailed about how to build an In car PC from the beginning - Damians style is VERY good - He explains things well - even to those with a non-technical background.
One of the challenges of doing this might be Touch Screen integration and of course it would be harder to retain that stock look.
Another book on the subject is "Build your own Car PC" by Gavin D J Harper. This book is a lot less technical and a LOT less detailed.
Obvioulsy building it yourself would be a much bigger project - it would be a challenge to retain the stock look - it may even be more more expensive.
You would need to install Specific software that is suitable for road use. If you are of a technical nature you may enjoy the project.