I frankly think that the best solution would be a panel mounted GPS
with battery backup. I have practiced under the hood and I can keep my
plane level with just my IFR GPS when in Track Up mode, the line moves
right and left with the plane, keep the line straight up and the plane
is not turning. Display the altitude and you can keep a rough pitch
also. Needs to be panel mounted so it is always there and ready. It
doesn't have to be one of the panel mount IFR GPS's, you could fashion
a panel mount for a handheld. But the key is to have it on, on track
and ready. If you get an electrical failure in IMC you aren't going to
be able to set anything up. ALL you attention will be needed keeping
the plane wings level.