Always-available input through finger instrumentation

A method for detecting when a finger is touching a surface, comprising:

• capturing images of the surface via a device worn on the finger;
• detecting, based on at least an analysis of a first image of the surface captured via the device, that the finger of a user wearing the device touches the surface, wherein the analysis of the first image comprises an analysis of only a first sub-region of the first image;
• and
• in response to detecting that the finger of the user touches the surface:
• transmitting the first image to a computing system to determine an executable action based on only a second sub-region of the first image, wherein the second sub-region of the first image is different from the first sub -region of the first image.

Anon-transitory computer-readable storage medium storing instructions that, when executed by a processor, cause the processor to performing operations comprising:

• capturing images of a surface via a device worn on a finger;
• detecting, based on at least an analysis of a first image of the surface captured via the device, that the finger of a user wearing the device touches the surface, wherein the analysis of the first image comprises an analysis of only a first sub-region of the first image;
• and
• in response to detecting that the finger of the user touches the surface:
• transmitting the first image to a computing system to determine an executable action based on only a second sub-region of the first image, wherein the second sub-region of the first image is different from the first sub-region of the first image.