Can I use a Wii MotionPlus remote as a mouse in Windows 10?

You'll need a combination of sensor bar and Bluetooth adaptor, like the one mentioned here: dolphin-emu.org/blog/2014/08/23/dolphinbar-review/

As for a specific program to use on Windows to make it work like a mouse, Instructables has these instructions:

1. Get a Wiimote (of course); WiiMotionPlus (actually is built into some new Wiimotes!); Bluetooth (either an adapter or built-in); the Glove_Pie and custom Wiimote program, and a Wii Nunchuk. Note: If the .PIE files are downloaded as .TMPs, you'll need to download them in Internet Explorer and copy the text into Glove_PIE.
2. First, download the files from step 1 (no viruses, I promise!) and open the Win-Zip file. Save all the contents to your computer. Run the Glove_Pie application. Save the WiiMotionPlus Mouse file to your computer and open it with Glove_Pie.
3. Connect the WiiMotionPlus and Nunchuk to the Wiimote. Next, open your Bluetooth software. On Windows Vista and newer, just type "Bluetooth" in the start menu search bar. Click on "Bluetooth Devices". Press 1 and 2 together on your Wiimote and click "Add New Device". Keep pressing 1 and 2 until your computer lists the Wiimote as a device to install. Select the device. At the next screen, click "Don't Use Passkey" and hit "Next". Your computer will install the Wiimote as a usable device.
4. Once the Wiimote is connected, open the Glove_Pie program and place the Wiimote flat on your work surface. Hit 1 and 2 on the Wiimote and click "Run" on Glove_Pie. The 1 and 4 lights on the Wiimote should light up. Once the 2 and 3 lights are lit, it is ready to use.

5. Ignore what Glove_Pie says about the controls. Instead:

   • Hold B and move the remote to move the cursor.
   • A is left click.
   • + is right click.
   • - is Esc.
   • Home opens the Start Menu
   • 1 is Space
   • 2 is Enter
   • The Nunchuk control stick acts as the arrow keys.

Check the Instructables link for updates.