I have used voicethread in the past and it was a great resource for students across all my classes to get involved with and collaborate. The problem with voicethread is that I didn't want to pay for it and I was only able to use the free version which only gave may a few uses.
You should be able to click on this link to see how I have used voicethread in the past. Most students typed an answer but they did have the option to video or audio an answer.
https://voicethread.com/share/4260972/