We are developing a technology that provides an objective measure of dehydration through a mobile smartphone application. This application would quickly and accurately calculate the capillary refill time from the finger of the patient (a proxy for dehydration) by using the smartphone camera and computer to record video and calculate the refill time. For the novice user, the application will instruct the user how to capture a video recording of the capillary refill time by placing the patient’s finger in view of the camera and performing the standard capillary refill exam. The computer will measure increments of change as small as one tenth of a second, much shorter times than the human eye can distinguish when health care providers perform this test subjectively. Normal and abnormal definitions of capillary refill time based on patient age, sex, race, and disease state would be built into the application algorithms. After the test is complete those algorithms will predict the level of dehydration and the suggested treatment based on the current standard of care. The technology is currently able to detect a fingernail and color from an image. Over the next 2 months our goal for the project includes measuring color change from a specified section of the fingernail and calculating the capillary refill time from a video image. Future work will include establishing a baseline capillary refill time in healthy subjects and then comparing that to patient’s with dehydration to establish cutoff values for abnormal results.