Rydberg atoms are an established platform for quantum technologies, with  new applications still emerging. Large dipole moment of Rydberg atoms  allows for their well-known interacting properties, facilitating e.g.  uantum gates. The same property also allows for detection of external fields, using transitions between two Rydberg states. Remarkably, these properties hold even in hot-atom vapor cell systems. I will present our results on detecting as well as transducing microwave and terahertz radiation into the optical domain. I will also discuss sensitivity limits, and show how we can achieve detection of thermal radiation, also in cryogenic conditions. I will also hint at ongoing cold-atom based experiments aimed at demonstrating ultimate quantum-metrological limits of sensing via collective qubit lifetime-extension techniques inspired by our past experiments with quantum memories. Those approaches hold a promise to realise optimal sensing protocol, towards reaching the standard quantum limit.