They're actually very different: with Android you create what's basically a daemon server, no UI but does everything it want, while with OS4 you register against service (there are 7 service types to choose from) and the OS itself runs and manages it, calling your registered service hooks.
Android gives far more control, at the cost of more (programmatic) complexity and more battery life risks (a badly implemented daemon/service will kill your battery life quick, whereas on the OS4 since the OS keeps full control of the execution it has a much better shot at managing battery/power issues, and it can more efficiently handle multiple applications registering for the same service).
The part that is similar is the handling of non-multitasking-aware applications (regular applications in OS4, applications with no daemon in Android): they're simply frozen in RAM, and killed if memory pressure becomes an issue.