HelloSlide allows users to upload their Power Point Presentation (as a PDF File) and then type additional text to each slide and then HelloSlide will convert that text into audio text. This is a great option for visually impaired or lower reading ability students, or students who are absent and miss your class, therefore missing the extra conversation you might give with your presentations. You could also use this for translating language in presentations if needed.
For a lot of teachers when they have a substitute they go with alternative plans because of the subs inability to give a lecture or "teach" the lesson. HelloSlide would provide teachers a way to allow a substitute to teach the lesson still.
Also, I don't necessarily like hearing my own voice (when recorded) so I can use this site to still provide audio to my presentation without having to record myself and then fix any mistakes. To create an account for HelloSlide, all you would need is an email and a password. It does require email verification which could prove to be difficult for student use. Also, the voice for the service does not have as much "computer" voice in it, and sounds more "natural."
The service is free and there are pay options available. The Free option provides users the opportunity to upload up to 50 presentations. The pay features provide exporting to video and auto translation if needed. Without export you do have to show the presentation through the website. Animations you use are limited, so that might determine how you add those to a presentation. You can decide to make your presentation public or private as well, meaning that you can search through Public presentations.
For more information, I recommend viewing the FAQ Page.