The discordant results observed among HIV PrEP clinical trials clearly indicate the importance of adherence in determining successful prevention outcomes . Sustained, topical delivery of ARV agents and microbicides using IVRs has been suggested for improving adherence; however, clinical data to support this assertion are limited [20, 21]. Real-time assessment of adherence during IVR clinical trials could allow quantitative measurement of the relationship between IVR use and HIV prevention efficacy. Until recently, no methods for real-time monitoring of IVR adherence had been reported. Boyd, et al. demonstrated proof-of-principle for using IVR temperature as a surrogate measure of adherence . They employed a commercially available temperature logging device inserted in the vaginal cavity to continuously monitor device temperature, and compared it to intravaginal (body) temperature to determine periods of device insertion and removal. These devices store over 5000 temperature measurements for later retrieval and have a measurement accuracy of 0.2°C. The data collected during a 7 day macaque study using these devices embedded in segments of silicone tubing showed that device temperature can accurately track insertion and removal patterns even in the presence of normal vaginal temperature fluctuations. The $340 cost per device, however, limits the ability to incorporate these devices into IVRs for widespread use, particularly in resource-limited settings. Additionally, these are specialized devices from a single vendor, with a risk of limited availability due to market or other circumstances.