What is the purpose of a Rosary? I am not Catholic and I am pretty sure the Rosary is mainly a Catholic artifact, and in modern times devout Catholics seem to always have a Rosary (as in, you know they're Catholic because of the Rosary).

My question is what is the purpose of the Rosary? 

(And as a non-Catholic Christian, should I get one?)
The Rosary is a very old artifact indeed and has evolved in time, the actual form of the Rosary is not what it was in the very beginning.

Rosary is a style of mental prayer that is based on repetition. This has been a tradition for many centuries since the early ages of monasticism. The emphasis upon repetition of brief, monologistic, prayer formulae laid the foundations for later monastic prayer traditions such as the Jesus Prayer and is the background for analogous forms of devotion in Latin Christianity such as the Hail Mary and Rosary.  (Columba Stewart OSB) 

The modern form of the Rosary may took its form when Domique de Guzman preached in favor of it. This also led to the story that the Virgin Mary delivered the Rosary to Dominique.

In its actual form, the purpose of the rosary is to meditate in its mysteries while repeating Ave Maria etc… Repetition is useful to achieve concentration and focus. The Mysteries of the Rosary are essential facts in the life of Jesus, except for the Assumption of Mary and the Coronation of the Blessed Virgin which are related to very old church traditions. It is not the purpose of the question to explain all of the mysteries, but a full list can be found in wiki. Meditation in the mysteries of the rosary is something that most christians do but in different ways (reading/studying the Bible, public preaching etc).

Probably you should not get a Rosary. If you want one, or you are curious about this type of prayer I recommend you to read the article or Steward (link above) in order to have more insight in this form of prayer. Then you only need to pray the Rosary and get used to it. Maybe you'll notice how the grace sheds a new light upon the mysteries of our faith.