Drawing or dragging an object on a mobile device is annoying today because the latency is manifested spatially with an obvious gap between the touch point and the line head or dragged object. This work identifies the multiple synchronization points in the input to display path of modern mobile systems as a major source of latency, contributing about 30 ms to the overall latency.

Mobile systems are equipped with a diverse collection of I/O devices, including cameras, microphones, sensors, and modems. There exist many novel use cases for allowing an application on one mobile system to utilize I/O devices from another. This paper presents Rio, an I/O sharing solution that supports unmodified applications and exposes all the functionality of an I/O device for sharing. Rio's design is common to many classes of I/O devices, thus significantly reducing the engineering effort to support new I/O devices. Our implementation of Rio on Android consists of about 7100 total lines of code and supports four I/O classes with fewer than 500 class-specific lines of code. Rio also supports I/O sharing between mobile systems of different form factors, including smartphones and tablets. We show that Rio achieves performance close to that of local I/O for audio devices, sensors, and modem, but suffers noticeable performance degradation for camera due to network throughput limitations between the two systems, which is likely to be alleviated by emerging wireless standards.

A user nowadays owns a variety of mobile systems, including smartphones, tablets, smart glasses, and smart watches, each equipped with a plethora of I/O devices, such as cameras, speakers, microphones, sensors, and cellular modems. There are many interesting use cases in which an application running on one mobile system accesses I/O on another system, for three fundamental reasons. (i) Mobile systems can be in different physical locations or orientations. For example, one can control a smartphone's high-resolution camera from a tablet camera application to more easily capture a self-portrait. (ii) Mobile systems can serve different users. For example, one can a play music for another user if one's smartphone can access the other device's speaker. (iii) Certain mobile systems have unique I/O devices due to their distinct form factor and targeted use cases. For example, a user can make a phone call from her tablet using the modem and SIM card in her smartphone.

Modern mobile systems are equipped with a diverse collection of I/O devices, including cameras, microphones, various sensors, and cellular modem. There exist many novel use cases for allowing an application on one mobile system to utilize I/O devices from another. This video demonstrates Rio, an I/O sharing solution that supports unmodified applications and realizes many of these novel use cases. Rio's design is common to many classes of I/O devices, significantly reducing the engineering effort to support new I/O devices. Moreover, it supports all the functionalities of an I/O device for sharing. Rio also supports I/O sharing between mobile systems of different form factors, including smartphones and tablets.