I've looked into this before, and TiVo is the ONLY device that accepts CableCard and output to HDMI. There is no competition. Everything else is a tuner, that outputs to your network, which is not same because it requires a PC to receive the signal.
I have a used, non-subscription, TiVo box that allows me to watch Comcast TV through a CableCard. The benefit is that I can watch local channels in HD through the TiVo. If I used a Comcast box, I'd have to pay extra for HD programming and an HD box.
I guess this Roku app would now be an alternative to that hack.