I second this recommendation for Insight Timer. I just use it as a timer that’s nicely customized for meditation, though it has guided talks and recordings that others may find useful.

The timer is MUCH better than the built in iOS timer. It has pleasant (less jarring) bell/gong sounds and customizable presets.

It also keeps track of your sessions which is useful as a subtle nudge to keep a routine practice.

It’s not essential but is nice, useful and free.