Push to talk historically has been a staple of a loyal sector of field workers and emergency personnel. This year, however, the technology’s biggest advocate, Sprint Nextel, has been trying to push it to the mass market with the promise of new features and a faster network. Meanwhile, coming at the technology through an application-centric approach, instant-messaging provider Palringo may quietly beat the wireless carrier to the punch.

The vendor this week introduced a P2T application for iPhone users, providing the voice equivalent of text messaging free of charge through the iPhone App Store. Palringo’s suite of communication mechanisms now lets users send text, picture, short message service, e-mail and instantaneous voice messages to their lists of contacts. The operator-independent app also works on other handsets, including BlackBerrys, Windows Mobile devices, Symbian and Java-based handsets from HP, HTC, LG, Motorola, Nokia, Samsung and Sony Ericsson, and now the iPhone. The Palringo service integrates with numerous IM platforms, including AOL’s AIM, Google Talk, Yahoo! Messenger and iChat, Apple’s IM client.

P2T has received mixed reviews, especially as a consumer application intended for wide-scale adoption. Nextel pioneered the market and met with great success when its sole focus was business users. But when the operator joined forces with Sprint and attempted to take the product mainstream, the brand failed to attract new users and also lost many of its existing subscribers as they abandoned it for text messaging, concurrently rising in popularity.

Sprint, which recently launched its P2T service over its CDMA network, is still positioning its technology for use in emergencies and in the field, but it is hoping to widen appeal by increasing its focus on “push-to-X” features. For either a monthly subscription or pay-per-use model, Sprint P2T users can also push out their e-mail, pictures or contact information. Sprint also has promised other push-to-X features within the year, including push to text, to locate or to get more info. At the end of last month, Verizon also unveiled its first phones incorporating an upgraded P2T service that combines voice over IP and CDMA 1x EV-DO Rev. A technologies. The Motorola-developed technology is designed to accelerate call set-up times and expand the P2T call capacity, now available in all of Verizon’s Rev. A markets.