There are lots of ways to record students nowadays, but is a website which works well for students who don't like being filmed, and also has a nice text-to-speech functionality if they want to compare their pronunciation. 

You can record your own voice, or type the script and assign a specific accent for the text-to-speech recognition. I've recently used this to provide the context for a lesson on passive forms. I made a newsreader who gave a report about a zombie attack on the college (...was attacked, were hurt) and used it as a dictogloss for the students - they had to listen while noting down as many words as possible, then they worked together to try to reconstruct the report. If your students have access to computers, they could create their own.