Can't help you with the smartphone question, but I have been to the Great Barrier Reef (about 2 years ago) and can offer a qualified opinion on that...
It is true that the GBR has been suffering a bit from...well, a combination of things: 1) being "loved to death" by tourists (like any other mass tourist destination in the world, from Stonehenge to the Pyramids to the beaches of Hawaii). All those people have an impact. 2) Various localized environmental issues (runoff from the land, agricultural chemicals, pollution, etc.). 3) Coral reefs worldwide have been been impacted to varying degrees by environmental changes (including, but not limited to warming ocean temperatures, ocean acidification, and more) - some places have been hit harder than others, and things are constantly changing.
So, all the above said, the GBR has indeed suffered somewhat. But the GBR is a huge thing (you can see it from space!), and it has not all been impacted to the same degree. There are places on the GBR that have taken more of a hit than others. As you might guess, the places that have been impacted most are (generally) closest to land and population centers, the easiest to get to, and the most popular tourist destinations - probably right where a casual tourist is headed: Cairns. If you/your mom has the option, get away from the mass tourist destinations (Cairns). I went on a week-long scuba trip on a boat that LEFT from Cairns, and the boat headed to the more remote, outer reef locations. The conditions there were quite good (at times really great). The problem, of course, is that 99% of the visitors do a day trip out from Cairns, and everyone goes to a small number of places. Those places are suffering most. To see the reef at its best, you need to go somewhere else - and that "somewhere else" is not quick/cheap/convenient for the average casual tourist. When we were 3 days out from the mainland, the reef looked awesome, healthy, full of life, pretty much everything I had hoped for - and I am very, very spoiled from doing scuba diving trips to some VERY remote, VERY pristine, untouched corners of the world. Which raises an important question...
Where else has your mom gone snorkeling? It's important because if she has only done this a little, she has probably never seen anything even close to a healthy tropical reef (most of the easily accessible reefs in the Caribbean, for example, are very badly damaged). If your mom has done lots of scuba diving in remote corners of, say, Indonesia, New Guinea or Micronesia, well then she might be disappointed at what she sees on a day snorkeling trip out of Cairns. But if all she has ever seen is a reef at a major tourist destination (cruise ship destinations) - or if she's never gone snorkeling before at all - then she will probably think the GBR is everything she had ever dreamed it could be - it's all relative to what you've seen before.
Most of us don't get to go to Australia very often. She's going. It would be a real shame to go there and skip the GBR. My suggestion would be to try to get away from the mass tourist spots (Cairns especially) if she can, and visit some other corner of the reef. But that takes time/money/effort, all of which are usually in short supply on a once-in-a-lifetime trip to the far side of the world. Yes, mom should go snorkeling on the GBR, hopefully she can invest a bit of time to get to where its truly great, but even if she can't, don't skip it altogether. Better to see it even if it's a bit compromised than miss it entirely because its not as perfect as it was 20 years ago - the same is true of so many popular places, no?
Hope that helps. Cheers.
