This paper reports on experimental trials with an Under Mattress Bed Sensor (UMBS), an easily deployable, non-contact, low cost alternative to the actigraphy watch for sleep monitoring. Results from a home-based study of elderly subjects confirm accurate temporal resolution of activity monitoring in bed. UMBS activity classification thresholds were determined by maximizing Matthew's Correlation Coefficient between the activity data captured using an actigraphy watch and the proposed sensor. Preliminary results on a healthy young subject showed very high agreement rates justifying its use as a replacement for wrist actigraphy.