Manual is the way to go. I work as an EMT and have gone to numerous calls when people use auto cuffs and think it is high. Then we show up and do it manually and they are generally is a normal range for themselves.
When we show up at the ER and their expensive auto machines take it and it reads high they will sometime check manually to verify the high readings.
Easy to learn and a scope and cuff together will be cheaper than and automatic one.