Unfortunately, just like PC DVD burners, a Blu-ray burner does not include any on-board audio or video decoding, let alone any way of hooking one directly to a TV. When installed in a PC and playing a Blu-ray movie, the actual video decoding is carried out by the CPU and graphics card (e.g. hardware AVC HD acceleration) and the audio is decoded by the sound card. Even the Blu-ray playback software runs on the PC itself. The only thing the Blu-ray drive does while playing a disc is read the data from the disc.
One option would be to get a compact barebone PC with a single IDE bay, a CPU capable quick enough for Blu-ray playback and a HDCP capable DVI or HDMI output. Then install the Blu-ray IDE drive in this along with the necessary hardware (RAM, HDD, etc.) & software (Windows, Blu-ray playback software, etc.) and hook the PC up to your display and speakers. The problem here is that by the time you get all the hardware and software, you'll have spent far more than what you would pay for an entry level set-top Blu-ray player.
Unfortunately, unless you already have an existing PC powerful enough for playing Blu-ray movies and don't mind using it for the television, your cheapest option would be to get a dedicated set-top Blu-ray player.