The short answer on CPU compatibility proper is that the Newton devices used the ARMv3 family CPUs (you'll find some ignorant references claiming that the Newton was "ARM 6", but "ARM6" isn't the same as "ARMv6". "ARM6" was a family of ARMv3 CPU... confused yet?) whilst some ARMv6 CPUs, as used in some now quite old cell phones and tablets, can be configurable to run in an "ARMv5" compatibility mode which itself is mostly compatible with ARMv3... with the *very large* caveat being "configurable to run"; an OS kernel designed for an ARMv3 isn't just going to work out of the box. (Note that there are some things supported by ARMv3 that are *not* supported however, like "26 bit" code; I have no idea if the Newton uses that, but if it does you're flat out SOL, that was depreciated after ARMv4.) ARMv7 CPUs, which you'll find in most "modern" devices, dispense with some of the more arcane features of the older architecture and need software to either to be recompiled for them or to use some heavyweight "trap and emulate" techniques for handling older code. It's possible to write a "clean" binary that'll run on all of them but it entails some pretty strict restrictions and old compiled code that predates ARMv7 is is pretty much guaranteed to break the rules. So... the short answer is that something using an ARMv5 or ARMv6 is the best fit you're going to fine for directly running Newton code but it's not a very good fit. IF one had access to the Newton source code it could undoubtedly be made to work "reasonably trivially" on a newer CPU but without it, no. (Unless the original code used the "26 bit" mode, in which case there's likely to be some major architectural changes needed and the resulting OS would almost certainly be unable to run any third party software compiled against the original Newton libraries.)
But all that aside... are you under the impression that you can just wedge a Newton binary into a modern phone and have it just magically work, setting aside entirely the question of whether the CPU is capable of executing the compiled binary code? Every single hardware device is different, do you think that the Newton OS is going to be able to magically figure out the new framebuffer hardware, digitizer, networking devices, etc? If you think that's going to work, well... before you do that, why don't you try yanking the ROMs out of a Commodore 64 and stuffing them into an Apple IIgs and letting us know how well that works? They both use 6502-family CPUs so clearly it should fire right up, no problem.