Sony are hoping to reinvigorate PS Vita sales around the PS4 launch as the two a "perfect partners" given the remote play features and various cross-buy titles.
It was recently revealed on the official PlayStation Blog that if you buy a PS Vita between and December 31 you'll get a redeem code for a free month of PS Plus simply by linking it to your Sony Entertainment Network account.
Also, if you register your new Vita you'll receive word on how to possibly win a PS4.