Update: Please note that this feature is only available for US users at the moment.
Since 2009; Google have supported visual voicemail so you can open the Google Voice app to view all your voicemails in text transcripts and play them on demand.
Google have now updated the mobile app so you can view and listen to your voicemails on demand directly from your call log on your Android phone. Your voicemails will appear alongside your outgoing, incoming and missed calls in your phone’s call log. you can access your voicemails as if you wanted to check the details of a missed call; just simply touch the voicemail and away you go. We’ve all had to go back into a voicemail to take a number down because we didn’t quite catch it – but this may be a process of old as there’s a new playback feature. You can slow down the recording of the message which is great if you’re listening out for that all important number or even speed it up if your listening to a long message!

To make use of this feature, download the latest app here and make the appropriate amendments under ‘Voicemail Display’ (settings). You must be using Android 4.0+ to apply this feature.