While Promptu is similar in function to Dragon Dictation for the iPhone, there are some true differences. For one thing, the application prompts subscribers to “train” the system by reading several individual paragraphs of text, in a process that takes about five minutes. Another difference is that users originate their text messages without leaving the Promptu application. That’s because the developers have figured out a way to use SMTP (Simple Mail Transport Protocol) to send the message as SMS text. The only disadvantage is that the recipient sees a fictitious number (like 001001100) as the return address. Nonetheless, responses to a Promptu originated message are displayed in a series of text balloons that resemble the threaded text messages in the iPhone SMS application.

As another differentiator, Promptu plays back the audio message it captured so that users have something to listen to while the service performs its transcription. Results are displayed on the phone’s screen for review. Corrections can be made and punctuation added by using the keyboard or by selecting the proper word from a “rolling barrel” of most likely matches. Adding the barrel selection to this ‘triage stage’ of message origination is a nice touch as well.

The rapid-fire introduction of speech-enabled mobile apps shows that the technology is coming of age. Now we are ready to learn if wireless subscribers are willing to pay for these services. Promptu is in a better position than analogous service providers to gauge whether a sufficient number of iPhone owners are ready to buy into speech-enabled messaging because it has attached a price (other than “free”) both to the core application and to the bundles of “Voice Credits”. The only other service that I’ve been using that makes use of the iTune store’s ability to support “top ups” or “refresh” of service credits is “kgb Answers” which sells “knowledge” on the iTunes store in packages of 2, 6 and 10 for $1.99, $4.99 and $7.99 respectively. That makes 2010 the year when we begin to learn the perceived value (in dollars or other local currency) for various mobile speech offerings.