Certain Sarracenia do well in live Sphagnum, as do some Nepenthes. Darlingtonia like live Sphagnum but I think they prefer it to be mixed with an airy aggregate like pumice. I think I read that D. rotundifolia likes it - I was surprised to find that, unlike my other temperate Drosera, they manage to keep pace with the moss. My Heliamphora also seem to like it, so maybe it's something common to all the Sarraceniaceae, but I don't have much experience with those so I won't say for sure. I'm doubtful that 100% Sphagnum would be appropriate for all species of Heli in indoor culture.
Peat works for Sphagnum - just make sure that some of the dead/dying ends of the strands are a little buried in the peat so that moisture is more accessible.
I typically dig a little depression and pat down the edges for starting Sphagnum to help keep shorter strands from drying out before they get established. Aggregate, like the pumice I mentioned, works even better; you can use pure peat at the bottom of the pot as it helps wick water but the part where the media meets your Sphagnum should be as much aggregate as possible; use just enough peat to fill in the gaps.
I recently got a big bag of very coarse pumice and had promising results in a pot where I put several cups of Sphagnum tips (cut from my other colonies) into a depression in the center of the pot (top layer of pumice mixed with enough peat and perlite to bind) and then about 40%-50% covered with more pumice. I did this at the peak of the summer heat, and about four months later all the gaps in between the top layer of pumice have grown in. I think that Sphagnum starts do better with a little bit of shade, and don't mind being somewhat covered by things like rocks and detritus. I bet it helps them hold moisture and raises local humidity.
You'll see the best rates of all, however, on an established Sphagnum colony. Sphagnum most prefers to grow on top of other Sphagnum.
~Joe