Transistor as remote power switch?

[Guitar42]

I have a design I'm working on that consists of two PCBs that are separated by 8 inches or so.  The main board has a microcontroller, battery charger IC, and other stuff on it.  The other board just has a few LEDs, momentary switches, and a slide switch for power.  I've got the main power running from the main board to the daughter board, thru the switch, and then back to the main board.  I'd like to not run main power to this daughter board, but I'd like to keep the power switch on the daughter board.  Is there a way to use a transistor on the main board that is controlled by the slide switch on the daughter board to turn on and off main power?  Ideally I'd prefer to run as little power to the daughter board as possible as I'm concerned about EMI.  I just don't have much experience with transistors as switches.

[Zero999]

Yes, a transistor is a possibility. Do you want to switch the high or the low side?

How about using a relay?

[Guitar42]

Probably better to switch the high side, but I don't think it matters.  I'd rather use a transistor than a relay mainly for space and cost reasons.

[Zero999]

What current and voltage?

Are there any other signals going between the two boards?

[Guitar42]

The board is running of a 3.7v lithium battery, about 800 mA. There are a few momentary switches on the second board and a few LEDs, all connected to a ATMEGA32U4.

[Zero999]

I'd go for a PNP BJT with lots of gain.
https://www.diodes.com/assets/Datasheets/ZTX788B.pdf
https://www.diodes.com/assets/Datasheets/ds31618.pdf

A P-channel MOSFET is another possibility but make sure you get one which can pass the desired current, with a gate voltage of under 3V. I had a quick flick through Mouser and found a couple:
https://www2.mouser.com/datasheet/2/308/NTR3A052PZ-D-1219532.pdf
https://www2.mouser.com/datasheet/2/427/72023-244672.pdf

[Guitar42]

Cool, thanks!  I was actually just looking at EEVBlog #262 and thinking that the schematic at the beginning of the video might fit my needs.  I have several momentary switches near the power switch and I'd rather not risk turning the device off on accident so I'm going to try it with the slide switch I currently have.  Do you recommend any of those 4 parts in particular for this application?  The NTR3A052PZ looks like it should be able to handle the load and voltage.