/My answer id not exactly about smartphones, but there definitely are smartphone apps which help with suggested activities (music, podcasts, books and audiobooks, meditation, diary) and I use a bunch of them during my commute./
When you are driving, you really don't want to be distracted from the road, so doing anything serious is out of question. You can use this time to relax - listen to good music, easy fiction or not important podcasts. The 2 latter choices are arguable, because they might distract your attention too much.
When you are being driven, you could do almost anything: read and answer to emails, make calls, plan something, etc. However, you are out of your convenient environment and this might not be very productive.
So any activity, which doesn't require intensive thinking, will do. In fact, transport is a great opportunity to do things which are important, but not urgent, and which lead to long-term results. I mean reading (not related to current work needs), meditation (if you like it) and updating your personal diary (thus thinking about your life).
When you are going home, a small meditation and relaxation will make you feel much less tired when you reach home. A good book might give you new perspective. And your morning drive is the best time to sum up your previous day in the diary - you don't need to write late at night any more.