Heterogeneity represents a singular barrier to the cross-domain adoption of sensor networks, limiting the take-up of Ambient Intelligence. Historically, the preferred approach has been to adopt a middleware solution to mitigate the problems associated with heterogeneity. Normally, the sensor discovery process is tightly coupled to the middleware platform, resulting in a unique implementation for each platform. Such an approach is unsustainable given the speed of developments in sensing technologies and the increased deployment of networks of sensors and Internet-of-Things (IoT) devices. An alternative approach is to decouple the sensor discovery process from the middleware and to regard it a discrete service that could be harnessed by different middleware platforms and external IoT services. This paper presents the design and implementation of a generic discovery service framework-POrtable Discovery Services (PODS). PODS utilises existing middleware abstractions to support heterogeneity in so far as such abstractions relate to the discovery process. An evaluation of the framework is presented using an exemplar middleware platform.