Anything greater than one is treated as plural, even if it is less than two, so 1.1 hours is correct, and so is "one and one tenth hours". A decimal fraction is treated as plural unless "of" is used, so "point eight seven hours" is correct, but it is "point eight seven ofan hour". Fractions such as half, one third, etc. take the singular: half a mile; a half hour; one third of a metre, etc.
"Half hours" is possible if it refers to multiple units of half an hour: "I have 10 half hours off every week".
1.1 hours (Hours are usually measured in quarter and half hours, or in minutes.)
0.87 hours (See above.)
1/2 meter (Meters can also be halves, and sometimes quarters--but are usually expressed in decimals. Example: 0.5 meters)
Hours may be measured in decimal fractions, for example in billing time (e.g. the legal profession where a unit of time is one tenth of an hour, and it is therefore convenient to refer to something like 0.7 hours in doing calculations).