We're big fans of the Remote Play functionality of the PlayStation 4 - being able to play PS4 games elsewhere in the house, either on a portable device or the PlayStation TV box soon to launch in the UK. However, when playing on a PS Vita's 5-inch screen, for example, it does diminish the gorgeous graphics of the new-gen games at times. PS4 games deserve the biggest screen possible.
Japanese company Gametech thinks it has the answer; a control pad with a 1024 x 600 7-inch IPS LCD screen that you insert your PS TV into and turn it into a much larger PS Vita.
The DekaVita 7 (which translates to "Huge Vita 7") has a "large-capacity" rechargeable battery that powers both the screen and the PS TV (or PS Vita TV in Japan) and a HDMI connection to take video from Sony's box. You can then access everything the PS Vita can through the large accessory, which is similar to Nintendo's Wii U GamePad in many respects.
There are caveats though. While it will work well for PS4 Remote Play, the PS TV has some compatibility issues with a large selection of PS Vita games. And it doesn't have a touchscreen, of course.
Also, at 23,000 yen (around £125) you might be better to get yourself a Sony Xperia Z3 Tablet instead, as that will also have Remote Play functionality and much more besides. Or even a second-hand Xperia Z2 Tablet - the screen will be even bigger then.