Preso.tv that allows you to broadcast your slides to the devices of everyone in a room with you. Not to be outdone, Prezi launched a similar option.
The latest update to Prezi allows you to remotely present your slides to up to 30 people at a time. To present a Prezi remotely select "present remotely" in your presentation's sharing options. Prezi will generate a remote sharing link that you should distribute to your audience. Through that link your audience can follow your slides on their laptops or iPads (Android option not available). When you move the slides, the slides move on the devices being used by your audience.
If you're already a Prezi user, the remote presentation option is nice. If you're not a Prezi user and you don't want to recreate existing PPT slides then Preso.tv is probably a better remote presentation option for you.
Applications for Education
Using remote presentation services is a good way to keep your students on the same slide that you're projecting. Likewise, remote presentation services provide a good way for students to share with classmates.