If you have reasonably good manual dexterity and good hearing, they are quite satisfactory. There is a huge variety of electronic devices now available. Most of them measure blood pressure from a cuff on the upper arm, the same location as with the mercury and aneroid devices. There are now some which measure blood pressure at the wrist, but the accuracy of these has not yet been adequately tested. Finger cuffs are also available, but are not very accurate.
Most doctors recommend using the arm cuff devices.
Most of the electronic devices on the market have not been adequately tested for accuracy by independent and trained observers who are not employees of the manufacturing company. To date, the device that has most consistently passed the criteria set up by these two protocols is the Omron HEM series. Consumer Reports described the results of their evaluations of several monitors in their May 1992 edition, although the exact testing criteria were not described. Their top rating was given to the Omron HEM 704C, the Sunbeam 7621 and 7650. A second Consumer Reports review is expected soon.