As far as I've seen reason/record do not support the APC 20 or APC 40 from Akai as a really useful input device. Both controllers send out standard midi messages like documented here: http://www.akaipro.com/apc40map
(the APC20 is just missing some of the APC40 controls).
I think that even though they were designed to work with some other software, they could be a very nice addition to a reason live performance setup. (e.g. starting DrRex loops, playing kong, programming Redrum, playing notes/chords on chromatic scales etc.)
Of course one can do some extensive remapping of messages with midiox to get a very nice setup but imho it would be even better, if Reason (5.0.2) would have some nice default mappings for those devices.