Nanomechanical resonators allow the boundary between classical and quantum motion to be explored and exploited. Suspended carbon nanotubes, vibrating like tiny guitar strings, are an outstanding experimental material because they combine low mass (leading to large zero-point motion), high specific stiffness (leading to large phonon energy), and high quality factor (leading to long coherence times). Until now, most measurements relied on electrical transport through the device, but optomechanical experiments exploiting resonant capacitive coupling to the nanotubes displacement promise higher sensitivity and the possibility to manipulate the mechanical state in new ways. I will show optomechanical measurements using a radio-frequency electrical circuit as a tuneable detector for the nanotubes vibrations. I will discuss potential for using nanotube springs as ultra-sensitive force transducers for nanoscale magnetic resonance. Finally, I will present a proposal to verify quantum behaviour in a suspended resonator by constructing an on-chip interferometer in which the entire nanotube, containing a million nucleons, forms the particle under test.