I use phone partners as a quick way to pair up students, and to ensure they aren't always paired with the same person!
To create phone partners, I usually cut and laminate these and give one to each student. I then use the Kagan Structure of Mix-Pair-Share (or walk around the room) to find random partners for the blanks. The students write each other's name in that spot, so later when I say they need to pair up with partner 4 - they can easily pull out their phones and meet up with that partner.
If it is laminated, students can rewrite other names in the blanks with dry-erase markers.