Does a "get" (Jewish divorce document) need to be written on a Klaf (parchment)?
And what are the halachic requirements to be a shaliach (agent) for a "get"?
May a man send a woman as his shaliach (proxy) and vise versa?
The material on which it's written can be just about anything (Rambam chapter 4):
על הכול כותבין את הגט, אפילו על איסורי הנאה; וכותבין על דבר שיכול להזדייף--והוא, שייתנו לה בעדי מסירה. [ג] כיצד: כותב על הנייר המחוק, ועל הדפתרא, ועל החרס, ועל העלין, ועל ידו של עבד, ועל קרן הפרה; ומוסר לה העבד והפרה או הנייר המחוק וכיוצא בו, בפני עדים.
The get can be written on anything ... even on a material that's not tamper-evident, if witnesses observe the delivery ... pre-erased paper ... clay, leaves, a slave's hand, a cow's horn -- in the latter case, the entire cow must be given.
Earlier (chapter 1) Rambam explained that the get must be complete as soon as it's written, e.g. you couldn't write it on a cow's horn, then cut off the horn and give just the horn. There's some discussion therefore about if it was written on a legal pad or piece of notebook paper, and then torn off/out. But the surface can theoretically be anything, so long as the writing is visible.
If I recall correctly from a discussion with Rabbi Notta Greenblatt shlit"a, common practice today is to use parchment paper (which is not the same as true parchment) because it's temper-evident, i.e. if someone were to go back and try to change a name, you'd be able to tell something is funny about the document.
The husband can appoint a shliach ("agent", "messenger", or "proxy") to deliver the get; the wife can appoint a shliach either to receive the get (effective as soon as the proxy receives it), or to accept it and deliver it to her (effective when she receives it). All of these proxies can be male or female, related or not.
From Rambam Geirushin Ch. 6:
הכול כשרין לשליחות הגט, בין שליח קבלה בין שליח הולכה והבאה, חוץ מן החמישה--הנוכרי, והעבד, והחירש, והשוטה, והקטן; ואם קיבל או הביא אחד מהן גט, אינו גט. [ז] אבל הנשים והקרובים, כשרים
All people are valid as Get proxies -- whether for receipt, delivery, or acceptance -- except for five categories: the non-Jew, the slave, the deaf-mute, the insane, and the minor.
My understanding is that today, the standard practice when a proxy is called for (as Rabbi Reiss said, either the couple live some distance apart, or they're within the same building but can't stand to be in the same room!) is to have a man serve as the husband's proxy to deliver the get all the way to the wife.
It says in halacha that only someone that knows Gittin well should be involved in them. A good sefer to look up is Kav Naki.
Chabad.org translates the Rambam on some of the laws of shlichus as it has to do with Gitton.
http://www.sofer.co.uk/html/gittin.html says that parchment is not required, and he writes with ¨Parchment¨ paper.