It's all kicking off in the Click To Call space.
Palo Alto based
Jaxtr has a widget that you can embed into your profile on MySpace, Friendster etc. This is again an implementation of "add your number and I'll call you". This at the moment all seems to be included under the banner of "click to call" although it's not
really. Not in the strict sense.
But in this context it actually makes perfect sense as it's a means of establishing telephone contact without having to give out your phone number (imagine this in the dating space too).
It includes voicemail and the ability to block people from contacting you.
Interestingly, LinkedIn founder Konstantin Guericke is at the helm.
Competing in this space is of course
Busta (and possibly Sitofono, although I don't know at the moment if that's available from within MySpace and it isn't free) which is attracting a following on MySpace, although that's a headset product which will attract a slightly different market.
This one is phone to phone:-
http://jaxtr.com/user/index.html