Garmin edge 705.. waterproof to IPx&... what does that really mean?
 

I know what the standard is... can with stand accidental immersion in 1 meter of water for 30 mins

but how does that relate to cycling in rain

I did a 3.5 hour ride last weekend and decided to pocket my gamin inside of several layers of clothing for safety concerns

would my garmin in theory been fine for a 3.5 hour ride in the wet ?

is there any type of case that is ipx8 that I can still mount on my bike so I could actually see my garmin ?

I've ridden with my 705 in a few downpours without problems, though not any 3+ hour ones, so I can't answer your question directly. I have owned wristwatches in the past where the manufacturer warned against pressing any of the buttons while the watch was wet. Apparently pressing a button breaks the seal in some case designs, but I don't know if this applies to the Garmin Edge (I hope not, that would be lame).

One thing I will say though, is that, IMHO, the memory card cover on the 705 seems like a huge water entry weak spot to me. The latch isn't very secure and I've had mine pop off a couple of times without me realizing it, including one time when I rode with it at least once before noticing the cover was missing (fortunately it wasn't raining, and I was able to find the cover later). It usually comes off when I have the unit in a pocket or bag, and probably accidentally press down on the latch when pulling the Edge out. I now keep some electrical tape over the cover (waterproof tape would be even better).

The 7 rating means you can drop your bike while crossing a river and the GPS will be OK.
The next rating down mean you can ride in torrential downpours.
The unit should be fine in anything.
6
powerful water jets
Water projected in powerful jets against the enclosure from any direction shall have no harmful effects.