It depends on style guides. Let me quote from Wiki on hypens..
<A definitive collection of hyphenation rules does not exist; rather, different manuals of style prescribe different guidelines. The rules of style that apply to dashes and hyphens have evolved to support ease of reading in complex constructions; editors often accept deviations from them that will support, rather than hinder, ease of reading.
The use of the hyphen in English compound nouns and verbs has, in general, been steadily declining. Compounds that might once have been hyphenated are increasingly left with spaces or are combined into one word. In 2007, the sixth edition of the Shorter Oxford English Dictionary removed the hyphens from 16 000 entries, such as fig-leaf (now fig leaf), pot-belly (now pot belly) and pigeon-hole (now pigeonhole).[3] The advent of the Internet and the increasing prevalence of computer technology have given rise to a subset of common nouns that might have been hyphenated in the past (e.g. "toolbar", "hyperlink", "pastebin").>>
<<Compound modifiers are groups of two or more words that jointly modify the meaning of another word. When a compound modifier other than an adverb–adjective combination appears before a term, the compound modifier is often hyphenated to prevent misunderstanding, such as in American-football player or little-celebrated paintings. Without the hyphen, there is potential confusion about whether the writer means a "player of American football" or an "American player of football" and whether the writer means paintings that are "little celebrated" or "celebrated paintings" that are little.[7] Compound modifiers can extend to three or more words, as in ice-cream-flavored candy, and can be adverbial as well as adjectival (spine-tinglingly frightening). However, if the compound is a familiar one, it is usually unhyphenated. For example, at least one style guide prefers the construction high school students, to high-school students.[8] Although the expression is technically ambiguous ("students of a high school"/"school students who are high"), it would normally be formulated differently if other than the first meaning were intended. Noun–noun compound modifiers may also be written without a hyphen when no confusion is likely: grade point average and department store manager.[9] When the modifier is an adverb ending in -ly or when one of the parts is a proper noun or a proper adjective, there is no hyphen (e.g. "a badly written novel" or "a South American actor").[10]>>
http://en.wikipedia.org/wiki/Hyphen worth reading. The point is, are you writing to meet the expectations of a particular style guide? If so, consult it on hyphens.
Does motion sensing need a hyphen?
2 answers
There's almost no way to tell for sure without seeing the whole sentence.