You want to make sure you get wireless MODEM jacks. Regular wireless phone jacks might not work. You can get the base unit that comes with one extension and then get extra extensions. Not sure how it would work for DSL though. I got mine at Circuit City for $40 and it works great.
if you get two or one each (vip622 and vip211) are supposed to have built in wireless phone jacks. you plug a phone in only one and the receivers talk to one another. they are so far the only receivers on the market that do this.