accelerometer that communicates with phone app

Device Description: The device should measure motion in three dimensions - with the most precise measurement along an axis perpendicular to gravity (define gravity as the z-axis and the axis of interest as the x-axis). The motion of the device will be pendulum like - thus the angle of the device relative to gravity will change. However, the distance measured along the x-axis should be independent of the angle of the device. The device will need to be capable of sending measurements to a cell phone app and robust enough to be moved between use and backpack-like storage without damage. Specifications: Accuracy: x-axis: 20 mm y-axis: 20 mm z-axis: 20 mm Temporal resolution: The device must send measurements at least every 50 ms Maximum Weight: 1 kg Maximum dimensions (mm): Unknown at this time App Description: The app receives measurements from the device at least every 50 ms. The app's algorithm computes when the device is at rest (movement of less than 10 mm/s over at least 1 second). When the device is determined to be at rest the screen turns green. Upon recognizing motion the screen turns white and displays (in the maximum possible font size) the total distance in the x-dimension that the device has moved since being at rest. This continues until the device is back at rest at which point the screen goes blank and returns to a green color. The app should also track and store motion in the z and y-axes during motion and should provide functionality to plot position as a function of time on all three axes after each trial (a trial is defined as the period between each period of rest). The app should also provide the option to plot the z position as a function of the x position.