Computers are being embedded in many of the devices that we use for our humdrum daily tasks. For example, it is common to find computers in ovens, watches, cars and phones. These computers can make a device more convenient or even make entirely new functionality available. This new dependance on computers raises new safety and security concerns; a buggy or malicious program may injure users have other costly consequences. We use microwave ovens as a case study to examine some security and software engineering issues that arise when mobile programs are delivered to computers embedded in appliances and similar devices. This is joint work with Rajeev Alur, Alwyn Goodloe, and Carl Gunter as part of the MiRL project: http://www.cis.upenn.edu/sdrl/mirl/