Wireless carriers AT&T and Verizon are now promoting the "open network" following the trend of high-profile tech companies vying to be seen as the "openest."

The mantras are everywhere -- from Nokia's "Open for anything" campaign to AT&T's announcement that it's the "most open." But the implications for mobile marketers, developers and consumers are still a bit murky.

AT&T uses GSM, which is the predominant network technology used by more than 80 percent of the mobile phones worldwide. The technology stores a user's mobile phone number and the related data onto a SIM card, enabling the user to take the SIM card and switch it to another device at any time. Conversely, users can take their handset and switch to a different network with a new SIM card.

As long as it's a GSM-compatible phone, a user can bring a handset from one carrier to another -- for example from T-Mobile to AT&T. The openness becomes less obvious for consumers when dealing with contracts, associated data charges and device-specific platforms.

For instance, consumers can only use their Apple iPhone on AT&T's network. Verizon's network is incompatible with the iPhone technology.

Some analysts have said that Verizon's move to open its network merely brings the company's offerings to the same level as providers using the more popular GSM network.

For manufacturers, the implications of Verizon and AT&T's decision may be clearer. Open networks may enable for the first time the manufacture of non-phone devices such as gaming systems or cameras for Verizon and AT&T.

Companies such as Hop-on, a developer and marketer of wireless phones and patented accessories and best known for developing the world's first disposable mobile phone, believe they will experience tremendous gains from new open network policies.

Hop-on has essential intellectual property rights to deploy GSM technology worldwide. The opening of these networks enables Hop-on to go after Verizon and AT&T customers with its new models of GSM and CDMA technologies.

Whether it's a truly fresh policy or just a marketing ploy, what is new is the desire of wireless carriers to be seen as the most open network. Clearly, what AT&T, Verizon and Google do other communications companies are bound to follow.