I feel like a lot of speakers nowadays, especially those at technical conferences, are aware that people just split their attention between presenters and their gadgets.
It's good to be aware of your audience, but not overly so. You can derail a good talk by misjudging your audience and making yourself look overly self-conscious and awkward.
You can even take advantage of it at some kinds of talks. If you assume some percentage of your audience has a device with internet access, give them some online supplementary material, or demo, or interactive data, or something similar to accompany your talk. There's a lot of nice stuff you can do on the web that's better than powerpoint slides.
I also tend to find that, at academic conferences, better questions come from people who're following along with the accompanying paper during the talk.
It's good to be aware of your audience, but not overly so. You can derail a good talk by misjudging your audience and making yourself look overly self-conscious and awkward.