As are touchscreen plotters located in the cockpit...
I recently sailed a V-42 in the Caribbean 1500, equipped with the LATEST & GREATEST Garmin touchscreen plotter/radar mounted on a massive Nav-Pod tower at the helm... (I know, don't get me started, a V-42 cockpit is small enough as it is... ;-))
Trying to use the stupid thing in any sort of weather was an incredible PITA. Attempting to open an AIS target, for instance, to acquire the information, often required a dozen or more separate "taps" on the screen, before one MIGHT finally work... Even with fingers that were completely dry, it seemed once the screen was 'contaminated' with any degree of moisture or salt air, it could become unworkable. And, on more than one occasion, while I had no luck clicking on an icon with my finger, a new one would be created by the inadvertent touch of the cuff of my foul weather jacket on the screen...
Final straw came during the last 2 nights of the trip, when dealing with some very heavy squalls. Despite being situated beneath a low cockpit bimini (don't get me started on THAT piece of crap ;-)) the heavy RAINDROPS being driven by the wind onto the plotter screen WERE LIGHTING UP THE SCREEN WITH NEW ICONS, WAITING TO BE SAVED AS WAYPOINTS !
UFB... But, I'm sure they work great at the display booth inside the tent at the boat shows...
With your "raindropped waypoints," it's little wonder I've recently started to see new plotters which offer both
push-button functionality. Hope there's still a push-button option by the time I may need to replace mine.
Just did Mark's suggested tap water test on my iPad2 and, to my surprise, it still worked! But mine is probably several generations old at this point, so YMMV. Besides, tap water is one thing, salt-encrusted could be quite another. I have several nav apps installed which all work well, but my latest fav is Polar Navy. The resolution in bright sunlight is not
good, but I mainly use it under the dodger or down below (as a secondary plotter), so not a problem. I hear the newer ones are better resolution-wise, but still probably not as good as a primary plotter. Btw, mine will shut itself down if its warm and exposed to direct sunlight, so if you're someone like me who prefers sailing w/o a bimini then take note. It recovers pretty fast once in the shade, but there's little warning. And yes, the nav apps will work offshore/outside of cell range, provided the tablet has a built-in GPS receiver. At the time I purchased my iPad2, this meant buying one with both wifi and
cellular capability, but that may have been an Apple thing.
There's also wireless integration available now, for example to allow you to transfer waypts., routes, tracks, AIS from your primary plotter to your tablet or phone, and vice-versa. Some of the Vesper and other AIS transceivers offer this capability via wifi. Not really convinced the transfer capability is really worth it, but it is now more easily available. Not sure about getting radar & AP to function on a device yet, but I'm sure it's coming.