An Apple Watch GPS-only model lets you carry out tasks like receiving text messages, answering phone calls, and receiving notifications when it's connected and in close proximity to your iPhone via Bluetooth or WiFi. GPS-only models are cheaper than cellular models.  A GPS + Cellular Apple Watch offers increased connectivity with the addition of built-in cellular. That means you can receive text messages, answer calls, and stream music — even if you don't have your iPhone with you. You just need to add the Apple Watch to your current carrier plan. Most carriers charge $10 a month for an Apple Watch cellular plan.