Hmm, equivalent to a 4th level power, ML 7th?
Sure, I'm OK with either.
Oh, and I think we should say what action it requires, like an Astral Construct's psi-like abilities:
Death Throes (Ps): If a walking egg is killed, its dying mind lashes out with invisible beams of psionic energy as a free action. All creatures within 120 ft. of the walking egg that have hurt the walking egg within the last hour are automatically hit by a beam for 4d4 points of force damage. These unerring beams do not need line of sight to hit their target, but do require line of effect. This is equivalent to a 4th-level psionic power (manifester level 7th).
Alternatively, we could make it (Su), then we wouldn't have to worry about manifestation levels.
Come to think of it, if the Death Throes is a psi-like power it'll have to make a Concentration check to manifest it when it's taking damage - which is pretty much a given
when it's dying violently.
So, we should really change it to supernatural, and change the
Wingless Wonder's Death Throes too (Su) as well:
Death Throes (Su): If a walking egg is killed, its dying mind lashes out with invisible beams of telekinetic force as a free action. All creatures within 120 ft. of the walking egg that have hurt the walking egg within the last hour are automatically hit by a beam for 4d4 points of force damage. These unerring beams do not need line of sight to hit their target, but do require line of effect.