Use iPhone on external screen with multi-touch Best thing about the iPhone is that it fits into my pocket which makes it easy to take everywhere.  But from time to time, it would be convenient to view  content on a bigger, tablet sized screen.  E.g., reading a kindle book on the train or scrolling through sports scores during breakfast.

Is there something like a "dumb tablet" that would allow me to use the iphone on a bigger screen?  

So something that would go beyond an external display (a.k.a. "mirroring") or a device that simply magnifies the screen. It's critical to be able to use the multi-touch functionality on the bigger, external screen.  Wireless connectivity (e.g., Bluetooth) would be ideal but a wired connection could also work.

TL;DR: the goal is to be able to use the iphone on a bigger, external screen from time to time without a full fledged 2nd tablet.

Thoughts?
AFAIK, this is definitely not possible. The closest thing to what you're describing would be AirPlay. However, AirPlay requires a newer Apple TV connected to a TV; it wouldn't work on an iPad or a Mac, let alone some cheap old Android tablet. Additionally, even if it were currently possible to mirror the display of your iPhone onto an iPad, that's all it would do is mirror the display of your iPhone; it wouldn't be able to respond to multi-touch.