voip ability encyption TLS SRTP , spying on Voip

Most voip gear these days is capable of some kind of encryption, typically SRTP and TLS.If you're using a provider that doesn't always stay in the media path you can encrypt call between similarly capable IP-based end points.There's some effort required to get the certificates issued and all the devices configured, but it can be done. I've been thinking that it would be cool to setup