Proximity-awareness, that is, a mobile device being aware of the presence and capabilities of other devices in its proximity, can be beneficial in many frameworks that support spontaneous sharing of sensors available in advanced personal mobile devices (e.g., smartphones and tablets). Providing Quality of Service (QoS) guarantees in such frameworks is highly challenging because of the dynamic and loosely coupled nature of Mobile Ad Hoc Networks (MANETs). A framework called the SPontaneous Information and Resource sharing InfrasTructure (SPIRIT) has been presented before to address the challenges of proximity-aware mobile sensor sharing. SPIRIT allows mobile applications to share sensors as services in an automatic fashion by enabling the service providers and clients to express a variety of QoS specifications. This paper presents a set of mobility-aware QoS mechanisms for enabling the implementation of QoS specifications along the multihop paths between service providers and clients in highly mobile environments. Simulations in small-scale Mobile Ad Hoc Networks show SPIRIT's ability to effectively control and manage traffic flows while maintaining desired QoS. The implications of the proposed QoS mechanisms extend beyond the scope of SPIRIT, as QoS provisioning is an important issue in many MANET frameworks and applications including Vehicular Ad Hoc Networks (VANETs).