I am not sure if a Value Stream is the right fit here since that monitors properties. Why not just use a regular stream? Have a service somewhere that takes in the results of their feedback and forms it into a stream entry. Perhaps you could elaborate on what you envision this mashup looking like for a more specific answer
I agree with Tori. You can use AddStreamEntry service of the Stream in your mashup. It also has the TimeStamp as one of the Inputs.
Please check the following link for more details on Stream:
Do let us know if you still face any issue.