I was interested in this as well- after some research, there just isn't much out there- ChannelMaster has a DVR for dual tuner OTA, I think it used to be owned by DishNetwork- it's about $300. No monthly fee-
They are kinda hard to find. I just sold my replay TV's, mostly because I am spoiled with the HD picture quality provided by DishNetwork DVR. I also just had U-verse installed, the jury is still out on how it compares-
AVS forum has some good information on these DVR's FYI.