My cousin recently bought a recumbent bike (well, I suppose it's technically a trike) and has been having a blast with it. I'd love to encourage her new hobby and get her an accessory for it as a Christmas present. Unfortunately, I know next to nothing about recumbents and what might be useful to have.
So, recumbent riders: what would you love to have or what do you find useful when you go out for a ride?
Update: My problem, specifically, is that I don't know what make/model of recumbent they have. So I'm looking for accessories that will work with all (or almost all) models. Not necessarily accessories that are exclusive to recumbents in particular.