All that sounds good.
I feel like we did a "sense territory" type SQ for one or more of the variant unicorns, but I can't find it with the CC down at the moment. Shade, do you remember where those are in the homebrew threads?
You're referring to the Psychic Warning Fence of the Brown Unicorn.
I'd considered that, but it didn't seem a terribly good match:
Psychic Warning Fence (Sp): A brown unicorn can use its horn to trace an invisible barrier of mental energies around an area of up to 1 square mile. The barrier warns any creatures with a psi-like ability, power point reserve, or telepathy that they are entering the brown unicorn's territory. A psychic warning fence lasts for 1 week, and can be dispelled as if it were a spell-like ability (caster level equals unicorn's HD). A brown unicorn may only have one psychic warning fence active at a time; creating a second immediately removes the first.
I think a variation of the Cariad Ysbryd's Lifesense makes better sense:
Lifesense (Su): A cariad ysbryd can mystically sense every living or undead creature within her territory (an area up to 5 miles across). If strangers enter her territory she immediately senses it. If a living creature is wounded or damaged within her territory the cariad instantly senses it.
As a standard action, a cariad ysbryd can link her lifesense to living or undead creatures within her territory, but to no more than 1 creature per Hit Dice the cariad possesses. This allows her to monitor the direction and distance to the creature(s) and any conditions affecting them: unharmed, wounded, disabled, staggered, unconscious, dying, nauseated, panicked, stunned, poisoned, diseased, confused, or the like. A cariad ysbryd can stop lifesense-monitoring as a free action; otherwise the monitoring will continue until the monitored creature dies, leaves the cariad's territory, or the cariad ysbryd is destroyed.
Any effect that opposes divination spells, such as the
nondetection spell, will also oppose a cariad ysbryd's lifesense. Lifesense can penetrate barriers, but 1 foot of stone, 1 inch of common metal, a thin sheet of lead, or 3 feet of wood or dirt blocks it.