Questions without か

This is a question I kinda wondered about for quite some time now, and I've always wanted to know how Japanese speakers would present a question without the particle か.

For example, if I said I got a new mobile phone, and then somebody wanted to say something like "...a PHONE?"...
(1) Would it make any sentence to say this as "ケイタイ" with no question or exclamation mark?
(2) If it does make sense, how is it distinguished as a kind of question or indication of surprise instead of a random statement? (e.g. "Phone.").

*EDIT* Not again, I forgot to do a search before posting a new thread...

*EDIT 2* Took a quick look at Omitting 'ka' particle from a question.. Just to confirm, would it be okay to use a question mark to indicate a question without か?

Because in Genki here, it says
.

Question mark is not really a part of Japanese language in terms of orthography, but question marks are quite common in daily life; it does help to disginquish ordinary statements and questions. (In speech, it is just like in English, you can make the difference with intonation.)
So it is not a problem to use "?" when you write in Japanese.

Alright. Thanks for the quick reply I believe I wanted to ask another question, but it seems I have forgot. It probably won't be too important until later on, though. Again, thanks.

Genki probably just meant that it isn't necessary to use か and ? together.

Just a note, while you can say ケイタイ？, it is quite common to use short questions which are noun + particle (verb drops off)

A: あ、田中くんからメールが来た！
B(1): 田中？
B(2): え、田中から？
B(3): 田中か...

I may be talking at least partial nonsense here, but to me, B(1) sounds like the speaker either didn't hear the name properly or doesn't know who A is talking about and is asking for clarification. B(2) implies the speaker does know who they're talking about but is mildly surprised that Tanaka sent A an email. B(3) isn't really asking a question of A at all (depends on tone, of course), but more talking to themselves (similar to そういうことか).