[civis]

I think that anyone may validly hear a confession in extremis if no priest is available.

[gbcdoj]

No one but a priest can absolve sins (cf. Council of Trent, Decree on the Sacrament of Penance). One could confess to a deacon or a layman, but he could not absolve, so it would be rather pointless.

[pgkdan]

I think that anyone may validly hear a confession in extremis if no priest is available.

Well I suppose anyone can hear a confession at any time, but if by that you're implying that anyone can also administer absolution you are incorrect. That is reserved for priests and bishops only. No matter what the circumstances.