What makes the phone go off?

I don't know, but here are some possibilities:

Consider who has her phone number:

1) Cheri's girlfriend, who, at the end of the convo in Cheri's room, says that she'll call back, but never does, though Cheri calls her back from the graveyard to begin framing Duffy.

2) The guy that Cheri was going to run away with had just talked to her on the phone, about one minute before, when she was in her car at the graveyard. She told him somewhat where she was, but not exactly. However, at the point that her phone rings, he should be outside his car and about to be on the run from the cop, except that he's talking to...

3) Cheri's mom, who is calling the police chief at that time, and then picking up Frank in town.

4) Aaron, who's dead.

5) Duffy, who's already in the cop car, in handcuffs.

6) Frank... Hmm... who has Cheri's keys and knows about Aaron's fate. He isn't back home yet. He is either chasing his dog, or in town burning his shirt.

Good question! I'll look into it further and get back to you...

I guess they just wanted to put Motorola in the movie :).

I'm almost sure that it was Cheri's boyfriend #4 :P

WoW! I know I'm posting on threads that are really ancient, but even all these years later in watching the movie it seems as though its still very unclear, to the viewer, what exactly the cell phone screen shown means.

In my realizing this movie is from 2003 I have to ask was text messaging even yet accessible from most mobile phones 11 years ago?.. I get that text messages were possible via cell in 2003, but I really don't think they were common knowledge to most and therefor not at all in regular use from most cell phones...

I will say that the very last scene when her phone rings/dings and then cuts to featuring nothing but Cheri's cell phone screen, it clearly reads, "Ready" with the time of "11:14pm" directly under the word "Ready". So, to me, it very much read as a text message saying, "Ready", that Cheri received while crossing the street.

So, what was it?.. A call?.. Or a text?.. And I guess for me that seems more important than who the actual caller/sender is...if it was a call, which seems more likely based on the era of the movie made(2003), why does her cell screen say, "Ready" unless that is the contact name that she has that particular person listed as on her cell phone contact list?

And I obviously don't know the answer, and therefor only listing two possibilities that it can be(call/text), along with my own rambling thoughts on was text messaging technology even in wide use at that time. And which of the two seem to be the more likely answer..lol

I guess it'll never be known for certain unless someone from the film is ever asked and answers the question about the movie's final, closing scene involving the cell phone screen.