Back in 2006 I helped build awareness around GrandCentral, now GoogleVoice. For me it was deja vu as I'd been a Webley/Comunikate user since almost when it started back in the late 90s, and had been using all kinds unified communications tools along the way. For me services like AT&T CallVantage, Vonage, PhoneGnome and just about every voice over IP service offered some twist on the idea of Find Me/Follow Me, where we could program multiple numbers as destinations for our calls and return them easily. But GrandCentral changed the game because first and foremost it was free. Second it quickly became the service you could set up as your voice mail for you mobile phone, and then as GoogleVoice, it added transcription and opened up to all comers.
Well pretty much all VoIP services now provide Find Me/Follow Me as a feature, but one thing GoogleVoice doesn't provide is a softphone client (officially) that you can use on your iPod touch, iPhone or iPad. Sure some of us who had Gizmo5 working with our GoogleVoice accounts prior to the purchase by Google of Gizmo5 have the ability to present our GoogleVoice number on outgoing calls using the Acrobits Gizmo client or even CounterPath's Bria for iPhone using our Gizmo credentials, but we're in the minority. Basically, GoogleVoice can bridge your calls with their web based app, which is something that's good for them, but really only appealing to the "I want only free calls" crowd. But I digress.
Real SIP based providers like Junction Network's OnSip, Aretta Communications (a client), CallCentric, etc., all provide services that offer many of the same functionalities as GoogleVoice within their unified communications suites. Setting up Find Me/Follow Me is easy too with most of them, but where each goes past GoogleVoice is in their ability to reach a wider range of end points, including the iPod Touch, iPhone or iPadsomething Junction Network's Mike Oath pointed out over a year ago when you add a softclient like did.
Over the past few days I've used my iOS devices more and more as an end point, and with the price of IP phones being what they are, these three are all far better values.