Soft and stretchable sensors and electronics hold great potential for application in wearable sensing, human-machine interaction, and soft robotics. On materials, double-network (DN) ionic hydrogels are a promising candidate because of their tunable mechanical properties, high toughness and stretchability, good conductivity, and excellent biocompatibility. Meanwhile, silicone-based elastomers like Ecoflex are commonly used structural materials for constructing wearable devices integrating ionic hydrogel-based sensing components. Moulding-based fabrication methods are limited for hydrogel-elastomer integration, inspiring us to develop 3D co-printing techniques for hydrogel-elastomer-based devices. Here we employ direct ink writing (DIW) for 3D co-printing of DN ionic hydrogel and Ecoflex, and adopt benzophenone (BP)-based chemistry to form covalent bonding of the two materials during cross-linking. We fabricate a wearable strain sensor and a sensory glove for demonstrations.