[3.5] Echo Skull

[Epinephrine]

We're playing with a restriction that we can only take two spells per level outside of the Player's Handbook, and I'll soon be picking 5th level druid spells (2 of them). Given how handy knowing things can be, I'm debating Echo Skull as a selection (1 hour per level duration, see/hear/speak through the skull, at any range).

Does anyone have experience using this, and how handy is it? Does anyone have any good ways to use this? I'm imagining leaving it behind us, to watch our back, combined with an Alarm spell from the ranger, for example. Or asking a wood wose to carry it ahead of us, to scout the path/dungeon. Or planting it in a room before a debate, or leaving it behind while I excuse myself from negotiations, and so on.

Does seeing something with it allow one to have Line of Sight, presuming that the target would be in range anyway (like around a corner and 20 feet over, for a medium range spell?) Even if it's not possible to use it that way, knowing what's going on is handy.