Vocaroo is a free, simple-to-use website that alows you to record voice messages which you can then send by email. Why not use vocaroo to send your student a message? All you need is a microphone.
Of course, you could ask your student to send you a recording. If they send you a message of about one minute in length that gives you enough information to assess their spoken level! You can listen to it on the website or save it on your computer.
You can also use vocaroo to make quality recordings while your student is with you. Vocaroo messages are saved on their website for about a month or you can download to your computer (in MP3, Ogg, FLAC or WAV format). Try it and let us know how you get on.
(On a technical note, you may need to set Adobe Flash Player settings to always allow vocaroo. Only bother if you have a problem.)