After a lot of internet research, this appears to be a common problem with most any year of Edge's. Thought I'd share for others that look here in the future. I have an '08 Ford Edge Limited w/ 75k miles.

Speedometer quits working and wrench light illuminates. If keep driving, the tire pressure not working icon comes one, then bit later the airbag icon comes on. When pull over, it will only work in low gear -- eventually won't go at all. When switch between P/R/D gears, car will have a big thump. This is the car going into fail safe mode to keep you from accumulating unaccounted miles. Had it towed to AAMCO. Note previously had similar issues, but corrected itself initially by turning car off and back on to reset the sensor causing the issue. Some also state that disconnecting the battery and reconnecting will help temporarily.

The issue is the failure of the output sensor located behind the transmission (feeds your speedometer, hence why you see this first). When you get this replaced, you might as well get the turbine input sensor replaced as well (others report them going out about the same time). The cost of the sensors are ~$50 each. However, the labor on dropping the transmission and replacing for me was ~$400 (used AAMCO, not the dealer, to save some money).

While a bit painful, better than it being the fault of transmission failure. Now fingers crossed to see a recall for it to get reimbursed. Again, very common problem in most any year edge -- typically saw occurring with others any where from 60k - 100k miles. I'd recommend addressing it when it first happens, as it will not go away -- and odds are you'll get caught somewhere you don't want to be when it happens next (out-of-town, night trip, etc).

Other than the CAM sensor failure I incurred at 30k miles, the car has performed outstanding -- love it...and we'll see how it continues to age.

Hope this helps someone in the future