Insulin pumps are small, portable devices used to pump insulin into the subcutaneous fat of a person with type I diabetes, also known as insulin-dependent diabetes mellitus. The first insulin pump was invented by Dean Kamen.
The pump is battery-powered device containing a reservoir for insulin, which is constantly pumped through an inconspicuous catheter that is placed under the skin. The catheter is replaced two or three times a week (the needle used for this is somewhat larger than that of a regular insulin syringe).
The insulin pump maintains a low dosage of insulin at all times, like a healthy person's pancreas. Additional doses of insulin can be issued by the user whenever necessary, e.g. when carbohydrates are eaten or drunk. Pump therapy, therefore, closely resembles natural insulin production in the body. See this node for additional information on the benefits of using an insulin pump.
An insulin pump works well with regular insulin, but for best results, a fast-acting insulin analog such as lispro should be used. In this case, the insulin can be taken when one begins to eat.
These devices are somewhat expensive (more than 3000 dollars/euros), but having one makes living with diabetes a lot simpler. Of course, if you are fortunate enough to live in a civilised country, the tax payers will pick up the bill. Even in countries where such soft-core socialism is frowned upon, medical insurance will most likely pay for your pump (it's a good investment, since diabetes can have expensive complications if not properly treated).
Pump manufacturers include Animas, Sooil, Deltec, Nipro, Lifescan, Disetronic (dominating the European market) and MiniMed (dominating the US market).