The PTV3000 is a handy accessory for the early adopters that will allow you to wirelessly share the content of your smartphone to an HD display.
The Push2TV adapter connects to a HD display that does not have Miracast built in (the vast majority of HD screens) and then pairs with your Miracast enabled device, such as the Google Nexus 4.
In short it means with a little extra expense you can utilise the features of the smartphone to their full potential.
The PTV3000 is due to arrive in the UK in early April, but the good news is that the hardware in the USA has just received an update allowing it to work with a much broader range of devices.
Thus from launch you should be able to use any of the following devices with the adapter:
- Samsung Galaxy S3 (Android 4.1.1 or above)
- Samsung Galaxy Note II
- Samsung Galaxy Note 10.1
- LG Optimus G (Android 4.0.4 or above)
- Google Nexus 4 (Android 4.2.1)
- Sony Xperia (various models with Android 4.0.4 or above)

Source: Android Central
Mark, I believe it will send at the resolution of the phone and scale accordingly.