tegami-bachi

Tegami Bachi (テガミバチ LETTER BEE, Tegamibachi?, lit. "Letter-Bee") is a shōnen manga series by Hiroyuki Asada. The series was first serialized in Monthly Shōnen Jump for ten chapters, and is currently serialized in the new monthly magazine Jump SQ..

The story takes place in the land of AmberGround, a place of perpetual night only partially illuminated by an artificial sun. Lag Seeing works as a "Letter Bee" (delivery boy) at the "Bee Hive" (a delivery service), with his Dingo, Niche, and her "pet", Steak, traveling with him. As a Letter Bee, Lag's job is entrusted to deliver letters and packages from town to town while avoiding Amberground's deadliest hazard — a species of giant armored insect known as Gaichuu, who attempt to feed off the "heart" that reside within these letters and packages.

The first ten chapters of Tegami Bachi were originally serialized in the now-defunct Monthly Shōnen Jump. A special un-numbered chapter was published as a one-shot in Weekly Shōnen Jump prior to the launch of Jump Square, where Tegami Bachi is now serialized.

Viz Media has licensed Tegami Bachi for an English-language adaption in North America, and serialized chapters in its monthly manga anthology Shonen Jump, beginning in its March 2009 issue. Serialization ended after the March 2010 issue, while the volumes have since continued to be released. In Europe, the series is licensed in Italy by Panini Comics under their Planet Manga division, and by Kana in France.

On February 16, 2009 a Drama CD was released of the Jiggy Pepper arc. It was named "Drama CD Tegamibachi" and has the ISBN 978-4-08-901167-6.

Source: Wikipedia

Honestly, this concept isn't unique. A Korean author produced a manhwa called Banya the Explosive Delivery Man years ago!

http://en.wikipedia.org/wiki/Banya:_The_Explosive_Delivery_Man