If you want access to encrypted channels you'll need a DVR with a cable card slot. You'll need to rent a cable-card from Verizon.
If all the channels you want are not encrypted, then any DVR with a QAM demodulator should work.
Of course, non-Verizon equipment will not have access to Verizon's guide, video-on-demand or any other Verizon services.
Enjoy.