Support 'cushion' for armchair?

Share your ideas about the practical side of caring.
Mum often dozes off in her armchair, either resting on her hand/arm and then her head keeps flopping back as the back of the armchair isn't very high. Any ideas on a good support cushion, or something that would make her more comfortable? The armchair is quite wide, so I wondered about getting one of those V shaped cushions?
Have you thought about getting a recliner? Great for snoozing in!
I like my V cushion for sitting up and reading in bed, but it doesn't provide much 'side' support. I have seen ones that seem to give more support like this one (google 'support cushion for elderly)