No, there is no way to limit that to your phone, not unless your cell provider would give you a static IP, which is unlikely.
Most VPNs are left open to the world because they have increased authentication requirements (lengthy PSKs, PKI authentication, etc) and can't be brute forced by traditional means. PPTP and SSL VPNs are an exception to that rule, but that's all part of the classic security-vs-convenience tradeoff.