It's possible to use students' mobile phones to provide a spin on the traditional icebreaking activities and games you play on the first day.
Using the picture gallery on mobile phones
Almost all phones nowadays come with cameras and most will have some kind of gallery program to allow you to view all the photos taken. For example this is how mine looks:
Here are some suggestions for how they could be used to add variety on day one:
Students work in groups of four. Two of the students hand over their phones to the other two and vice-versa and they go through their galleries and make guesses about who the people are (family, friends etc) and where/why the picture was taken. They then get back together with the other pair and find out if their guesses are true.
Alternatively the students, the students can work in pairs and they just look at each other's galleries and ask questions to learn more about them (who's this? Where was this picture taken?)
Another more extensive (and potentially invasive - make sure you get students' permission to do this first!) is to get them to look through eah other's phones to find out as much about each other as possible. So, for example, they could look at the music on their phone to find out their tastes, look at the gallery, contacts. These can then be checked with the person whose phone it is.