After going back and forth with a friend of mine over just how Warp Perception was supposed to work, I decided that the power simply giving Unnatural Senses to the psyker was too vague (Unnatural Senses is vaguely defined as a whole, and a lot of it comes down to interpretation and the specific creature that has the trait, but I'll leave it to someone else to tackle for now).

As a replacement, I came up with this effect that gives a more concrete definition of how the power works without changing any of its statistics. This has not been balanced or playtested at all, and is purely based on my interpretation of the fluff given.

Warp Perception

The psyker opens his senses to the Warp, allowing unnatural tendrils of energy to augment his own perceptions. His flesh no longer limited, he casts his gaze wider and hungrily scents prey from farther afield.

Value: 100 xp

Prerequisite: Willpower 35

Action: Half Action

Focus Power: Challenging (+0) Psyniscience test

Range: Self

Sustained: Half Action

Subtype: Concentration

Effect: The psyker is able to see the location of any creature or object with a warp-presence, with a radius of up to the Psy Rating multiplied by 10. Weaker presences may require a Perception-based test to see, while those with no presence at all (such as Untouchables or certain xenos) are unable to be found by this power.

What do you guys think?