What is the weight of the devices?
This depends on the configuration. In the latest version, the basic device (no battery or housing) weighs 8g. Battery weight depends on the battery size you wish to use. We currently use readily available single-cell lithium polymer batteries (3.7 V), and these come in a large range of weights from under a gram (20 mAh), through approximately 22g (1000 mAh) to hundereds of grams and above (e.g. 10 Ah cells). Selecting the appropriate battery size depends on the application, configuration, desired device longevity.
Housing depends on the deployment. We have experience of deployments and attachements on seabirds using heat-shrink tubing, which is waterproof and very lightweight (a few grams). However, researchers could deploy devices in a variety of different housings depending on the application.