Okay, I feel like an idiot for not knowing this but do those with blindsight have to roll perception to noticed hidden foes? Or like tremorsense, once they enter blindsight's field of vision the hidden foes are known about?
No.
Blindsense
Other creatures have blindsense, a lesser ability that lets the creature notice things it cannot see, but without the precision of blindsight. The creature with blindsense usually does not need to make Perception checks to notice and locate creatures within range of its blindsense ability, provided that it has line of effect to that creature. Any opponent that cannot be seen has total concealment (50% miss chance) against a creature with blindsense, and the blindsensing creature still has the normal miss chance when attacking foes that have concealment. Visibility still affects the movement of a creature with blindsense. A creature with blindsense is still denied its Dexterity bonus to Armor Class against attacks from creatures it cannot see.
Alright, thank you for clearing that up for me.
I really like Blindsense and Blindsight. The GM has to tell you if there's something invisible in your viewing range, which means you can warn the rest of your party and cast spells (i.e. glitterdust) to expose the invisible creatures.
Any spellcaster w/ Blindsense/Blindsight should have a Selective Spell Glitterdust and some Itching Powder (adds a DC 12 Fort Save to Glitterdust. Failed save = -2 on atttacks, saves, skill checks, and ability checks until opponent spends a round WASHING IT OFF (not likely in the middle of battle unless they have Create Water)) handy at all times, IMO.