Cynic
General stuff:
To play goldboxes on smartphone you need hardware qwerty keyboard (with arrows - not all qwerty phones have them). So iphone is not an option. Also you need quite advanced port of dosbox. I haven't tried Symbian dosbox ports for some years, may be they will work. Android has proper dosbox ports (multiple of them) so it suits well.
Personal experience:
I finished PoR and Curse, played some Secret (skipped it), finished one FRUA module, now playing PoD - all on mobile phone.
Hardware: Not a big list, I played on
this phone. Something weird with its price on Amazon though, I bought it for 220$ more than a year ago. Proper android phone must be qwerty with arrows, with horizontal screen (to display 320x200) and running android 2.2+.
This one should also work, but it has smaller screen. Both models are quite old. From newer ones
this may suffice but it has button instead of arrows and It cannot be bought online.
Software: Last time I checked (this summer) android has the only one really working dosbox -
anDosBox. Others don't work (like aDosBox) or a crippled fork of this one (DosBoxTurbo). I played with anDosBox but after some updates it added new menu screen and optional optimizations that crashes on my phone. So I requested sources of old version of anDosBox (they are GPL) and build it for myself. Changed name to DosBoxGPL and location of dosbox configuration file to not conflict with other dosboxes. I don't want to publish binaries (to not harm anDosBox authors) but if somebody want to use it - PM me, I'll send you APK (no piracy here - proper GPL usage). Also some of goldboxes (FRUA) will crash with default anDosBox settings, set "core=normal" in conf file (learn about that hard way debugging anDosBox sources).
Conrols: PoR and Curse - everything works (some operations need two buttons - not a problem with qwerty), PoD and FRUA - everything works except diagonal movement in battles (you must use touchscreen for them - not a problem, as not every battle need them).
Of course with qwerty android and dosbox you are not limited with goldboxes. I also played Ultima I, and some MM3 (it looks really great on small screen). Also tried many games, almost all 80-s games should work (e.g. U1 - U6), but 90-s games has more troubles from mouse control.
To play goldboxes on normal (not qwerty) phones you'll need quite advanced touch UI - they are unplayable with current dosboxes.