Base off this gist: https://gist.github.com/olivergierke/3215345 a small extension to avoid writing the checkout command, we store the hash in a variable then checkout the other branch and proceed with the cherry-picking:
[alias]
last = !git log -n 1 --pretty=format:%H $1
cp-last-to = "!sh -c 'HASH=`git last` && git checkout \"$0\" && git cherry-pick $HASH'"
So you can just do:
master $ git commit -m "$commitmessage"
master $ git cp-last-to dev
One thing to note is that after this command you will be in the other branch (dev in this case), ready to pull, push, or sort out conficts as necessary.