A travel-insurance policy to cover theft, loss and medical problems is essential. There are a wide variety of policies, most sold online; make certain your policy will cover speedy medical evacuation from anywhere in Indonesia.
Theft is a potential problem in Indonesia, so make sure that your policy covers expensive items adequately. Many policies have restrictions on laptops and expensive camera gear, and refunds are often for depreciated value, not replacement value.
If you are diving, specialist dive insurance is a wise investment.
Worldwide travel insurance is available at www.lonelyplanet.com/travel-insurance. You can buy, extend and claim online anytime – even if you're already on the road.