Ok...so it's not really an aftermarket navigation system as much as it is just a dash-mounted tablet, but it's the best I have right now.
I bought a Nexus 7 a few months ago (on a side note, I love the thing) and wanted a way to put it in my car for long road trips, like the one I have from NC to CA coming up in two days. The main reasons being:
1. A large, dash-mounted navigation screen.
2. An easy to view readout of text messages while I am on the road.
First, I purchased the app TabletTalk from the Google Play market, which ran $2.99 I believe (only need one copy for phone and tablet.) I set it up per instructions and had my Droid Razr communicating with my Nexus 7 via Bluetooth in no time. This way, when I am driving and receive a text, I can easily glance over and see who texted me and what they said. At that point I can either respond via the tablet or from my phone (once I get to a safe spot, of course.)
TabletTalk also has an option to readout who is calling you, which allows you to avoid picking your phone up while you're driving. Since I have only added really important phone contacts to my Crosstrek's Bluetooth system, now if anyone not saved in my car's system calls me, I can see their name pop up on my tablet and then decide if I want to answer via the Crosstrek's hands-free system or ignore the call.
Since my tablet is WiFi-only I then go into the Bluetooth settings on my Razr and Nexus and pair the two devices so that the tablet can share the phone's 4G LTE connection. I won't go into detail on this as each phone/tablet combo will probably vary.
Ok, so now I have the tablet communicating with my phone seamlessly and need a way to mount the tablet in my car. I headed on over to Amazon and after some searching and review-reading, I settled on the Arkon SM517 windshield mount http://www.amazon.com/gp/product/B00...s_o00_s00_i01.
The mount is extremely sturdy and holds on to the dash extremely well, as well as locking into whatever position you need it to be in without slipping.
I don't really need to get into details of how the mount attaches to the dash (self-explanatory) or anything, but just know I played around with a few options of where to place it until I found an area that doesn't obstruct my view and is easy to access, and I recommend you do the same.
So, there you have it. Now I have a simple solution for navigation, internet, texting/calling in my Crosstrek. The small, 7" tablet really doesn't obstruct my view out the windshield at all, but I am taller so maybe for shorter people it would be a bigger issue. It is definitely not something I will keep in my car every time I run to the store, but for longer trips it will really come in handy.