The Nexus 7 3G is out and I'm wondering whether Android 4.2 tablets are still data-only devices. Can I install a custom ROM or apk to this tablet so that I can send and receive GSM calls and text messages on it? If not, why not? What's missing?

Added: Nexus 7 3G has many hardware features of phones, but not all: It has gps, bluetooth, headphone jack, accelerometer, gyroscope, ambient light sensor, compass and nfc, but does not have a receiver (earpiece), haptic feedback (vibrate) or a rear camera. IF the 8"x5" tablet can be used as a phone, you won't look funny putting it against your ear because it has no earpiece.

Added: The question is about GSM calls and texting, not VOIP or SIP calls or tethering.