I agree strongly. That is just the type of thing to address in a cover letter. That said, a lot of employers are going to jump immediately to thinking about what it'd take to meet you in person. If it's a serious, salaried position, a lot of employers will go through the expense of flying you out. Many won't and search for local candidates because of that. I used to work in recruiting for a large company, and it's actually putting the recruiter in a tough spot to offer to travel on your own dime, as you're essentially putting the decision about spending hundreds of dollars of your own money in his or her hands. That's awkward for anybody. If you're really serious about it, I'd try to introduce the idea (sort of like you're saying with calling back) in a way that does not put the decision about the expense on that person. You also want to avoid desperation. I remember interviewing candidates now and then who happened to be passing through town (no big deal), but I wouldn't have asked them to do it and I would've felt miserable if I'd gone along with someone offering to fly out and then ended up not hiring them.
