I'm not sure if a wireless phone jack exist...do you mean you need a wireless router to connect computers wirelessly? If this is the case...Just purchase a wireless router and hook it up to the modem. Linksys makes a good product...
If you mean wireless phone jack as in these:
I am pretty sure the max speed is 33.6 so it would be slower than a 56K dialup modem
Copy and Paste from description:
Fully compatible with 56K v.90, 33.6K & 28.8K v.34 modems (maximum connect speed is limited to 33.6K in most cases). Ideal for the phone jack installations required for satellite TV receivers, WebTV, DVR systems like TiVo and UltimateTV, and all online service providers. It also passes Caller ID and Call Waiting, so you won't lose any phone company services. Does not interfere with X10 signals.
OK Just found this info:...........
I've got my computer in a room where there isn't a phone jack at the moment and have DSL. Can I get a wireless phone jack that would work with my DSL line? I'm about 60 feet away from the nearest phone jack in the kitchen.
Wireless phone jacks are a really neat technology, but they won't work for your intended purpose.
Wireless phone jacks work by using your home's electrical wires and outlets to bring a phone jack to a part of your house where there is none.
There are two parts, a base unit and a receiver.
You plug the base into an electrical outlet near an existing phone jack. You connect the phone jack to a port on the base.
Then you plug the receiver into any other power outlet in your home and plug the phone into the phone jack on the receiver.
In theory, the system should work with DSL.
When you get DSL at your house, you can connect the modem to any live phone jack.
But there simply isn't enough bandwidth to let you connect your DSL modem to the newly installed wireless phone outlet.
There is barely enough bandwidth to handle a dial-up connection, which is a great use for these devices. I know many people who use them with a TiVo or satellite receiver.
Your best bet to get that distant computer onto your DSL is to do it with 802.11 wireless networking.
You can use either a DSL modem with wireless capability built in or a separate wireless access point connected directly to your DSL modem.
Then you'll need a wireless receiver for your desktop computer.