"Jailbreak Your Voicemail ;P"
— Jay Freeman (saurik)
Over the last three years, I (saurik) have approached a number of companies (at conferences like CTIA) to help solve some serious "problems" I feel our unique Cydia community experiences with voicemail.
#1: Unlocks mean no Visual Voicemail
There are over a million unlocked iPhones currently using T-Mobile. That's almost 3% of their entire customer base... all without access to Apple's Visual Voicemail feature.
#2: Jailbreaking stops at the Device
Jailbreaking is great for devices we hold in our hands, but sometimes the systems we struggle with are services, not products. If "jailbreaking the carrier" were only viable...
#3: Voicemail is neither Flexible nor Fun
Here I must say: this is a personal problem I have, that I imagine bothers many others: listening to voicemail takes forever, and most people just say "call me back" (duh).
Years ago, I started using a transcription service called PhoneTag that offered "truly visual voicemail" (that is read, not heard).
(These days, a lot of users equate this with Google Voice, but the error rate is nearly unusable: 28% to PhoneTag's great 3%.)
So, when the iPhone came out, with their "visual voicemail", I had the same reaction I had to the iPhone itself: "great... but". :(
In trying to better solve these problems, I embarked on a quest to build a scalable VoIP hacking platform; in so doing, I was rapidly schooled by "per-minute charges".
Knowing that cost is a major factor for our community, I decided to concentrate on partnering with larger companies that had better negotiation positions in VoIP-land.
Most of the companies I found, however, were "one-feature wonders" (adding just one new idea, like voicemail transcription) that each charged "too much" per month.
Recently, however, I finally found what we needed: a company with a business model that lets them agressively add interesting features while still attempting to offer as much functionality as they can for free...
...and, maybe only exciting to me, they had just partnered with PhoneTag to offer their highly accurate voice transcription service.
However, from simple things like custom per-caller greetings to the ability to unmask blocked numbers (yes: bypass Caller ID block): there's something for everyone.
After installation: open up your normal Phone app, tap the new YouMail button in the tab bar, and you'll be guided through registering a YouMail account and activating this service.
Upon activating, you will have a new voicemail greeting, as well as text and email alerts when you receive voicemail.
Log into YouMail.com to customize your greetings and alert preferences (and for optional call features including voicemail transcription or ditching unwanted callers).
(You can deactivate YouMail at any time via "Settings" on the new voicemail list.)