As usual, good in theory, not so much in implementation...

The telecom company you plan to compete against owns the medium (the wires) and the transport (the bits that go across those wires). What makes you think that you can build a home electronics device that will work with their medium and transport if they don't want you to? (unless, of course, the laws in your country require it, and even then, you will face massive competition from those who have been doing this for decades)

If they use a public standard for broadcast (DVB, ATSC, etc) and if they don't use any encryption, you can *probably* build a digital receiver for the actual TV broadcast signal; but that doesn't mean that you can use the box to control any proprietary content, to control any server-side technologies, or to control and advanced services enabled in the bitstream.

Not trying to quash your dreams or anything, but I spent 15 years in this industry (here's my qualifications), and it's not as easy as waking up one day and saying, "I think I'll compete with the big boys today and either put them out of business or make them buy me out."

That said, let us know how it goes...