The authors describe the design and formative evaluation of a sensor toolkit for Android smartphones and tablets that supports inquiry-based science learning. The Sense-it app enables a user to access all the motion, environmental and position sensors available on a device, linking these to a website for shared crowd-sourced investigations. The authors describe the four investigations with the toolkit: environmental noise, sunlight levels, air pressure and rainfall, and the speed of lifts (elevators). These show a variety of methods to initiate, orchestrate and conclude inquiry-based science learning. Two of the missions are in the context of a study to develop a community of inquiry around weather and meteorology. The others are intended to engage members of the public in practical science activities. Analysis of the missions and the associated online discussions reveals that the Sense-it toolkit can be adopted for engaging science investigations, though the practical issue of calibrating sensors on personal devices needs to be addressed.