I created a number of mini sensor node boards using an attiny841 and a nrf24l01+. Originally I was going to write my own program using the RF24 library but just recently decided to use mysensors. Below is my code for a simple door/window sensor.

/**
 * The MySensors Arduino library handles the wireless radio link and protocol
 * between your home built sensors/actuators and HA controller of choice.
 * The sensors forms a self healing radio network with optional repeaters. Each
 * repeater and gateway builds a routing tables in EEPROM which keeps track of the
 * network topology allowing messages to be routed to nodes.
 *
 * Created by Henrik Ekblad <henrik.ekblad@mysensors.org>
 * Copyright (C) 2013-2015 Sensnology AB
 * Full contributor list: https://github.com/mysensors/Arduino/graphs/contributors
 *
 * Documentation: http://www.mysensors.org
 * Support Forum: http://forum.mysensors.org
 *
 * This program is free software; you can redistribute it and/or
 * modify it under the terms of the GNU General Public License
 * version 2 as published by the Free Software Foundation.
 *
 *******************************
 *
 * DESCRIPTION
 *
 * Simple binary switch example 
 * Connect button or door/window reed switch between 
 * digitial I/O pin 3 (BUTTON_PIN below) and GND.
 * http://www.mysensors.org/build/binary
 */


// Enable debug prints to serial monitor
#define MY_DEBUG 

// Enable and select radio type attached
#define MY_RADIO_RF24
//#define MY_RADIO_RFM69

#include <MySensors.h>
#include <Bounce2.h>

#define CHILD_ID 5
#define REED_SWITCH_PIN  3  // Arduino Digital I/O pin for button/reed switch

Bounce debouncer = Bounce(); 
int oldValue=-1;

// Change to V_LIGHT if you use S_LIGHT in presentation below
MyMessage msg(CHILD_ID,V_TRIPPED);

void setup()  
{  
  // Setup the button
  pinMode(REED_SWITCH_PIN,INPUT);
  // Activate internal pull-up
  digitalWrite(REED_SWITCH_PIN,HIGH);

  // After setting up the button, setup debouncer
  debouncer.attach(REED_SWITCH_PIN);
  debouncer.interval(2);

}

void presentation() {
  sendSketchInfo("Garage Door Sensor", "1.0");
  // Register binary input sensor to gw (they will be created as child devices)
  // You can use S_DOOR, S_MOTION or S_LIGHT here depending on your usage. 
  // If S_LIGHT is used, remember to update variable type you send in. See "msg" above.
  present(CHILD_ID, S_DOOR);  
}


//  Check if digital input has changed and send in new value
void loop() 
{
  debouncer.update();
  // Get the update value
  int value = debouncer.read();

  if (value != oldValue) {
     // Send in the new value
     send(msg.set(value==HIGH ? 1 : 0));
     oldValue = value;
  }
}

In the arduino IDE, I am getting the following errors when I try to compile. Before I start digging into the library files, is it possible to use mysensors with the nrf24l01 on the attiny841?

In file included from C:\Users\cdrum\Documents\Arduino\libraries\MySensors/MySensors.h:64:0,
from C:\Users\cdrum\Desktop\MySensors Sketches\WindowDoorSwitch_attiny\WindowDoorSwitch_attiny.ino:36:
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp: In function 'void clearPendingInterrupt(uint8_t)':
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp:73:2: error: 'EIFR' was not declared in this scope
EIFR = _BV(interrupt);
^~~~
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp:73:2: note: suggested alternative: 'GIFR'
EIFR = _BV(interrupt);
^~~~
GIFR
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp: In function 'void hwPowerDown(uint8_t)':
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp:96:19: error: 'WDCE' was not declared in this scope
WDTCSR |= (1 << WDCE) | (1 << WDIE);
^~~~
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp:96:19: note: suggested alternative: 'WDIE'
WDTCSR |= (1 << WDCE) | (1 << WDIE);
^~~~
WDIE
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp:117:18: error: 'WDCE' was not declared in this scope
WDTCSR |= (1 << WDCE) | (1 << WDE);
^~~~
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp:117:18: note: suggested alternative: 'WDIE'
WDTCSR |= (1 << WDCE) | (1 << WDE);
^~~~
WDIE
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp: In function 'bool hwUniqueID(uint8_t (*)[16])':
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp:277:31: error: 'OSCCAL' was not declared in this scope
*((uint8_t *)uniqueID + 3) = OSCCAL;
^~~~~~
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp:277:31: note: suggested alternative: 'OSCCAL0'
*((uint8_t *)uniqueID + 3) = OSCCAL;
^~~~~~
OSCCAL0
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp: In function 'uint16_t hwCPUVoltage()':
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp:299:2: error: 'ADMUX' was not declared in this scope
ADMUX = (_BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1));
^~~~~
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp:299:2: note: suggested alternative: 'ADMUXA'
ADMUX = (_BV(REFS0) | _BV(MUX3) | _BV(MUX2) | _BV(MUX1));
^~~~~
ADMUXA
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp: In function 'uint16_t hwCPUFrequency()':
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp:336:18: error: 'WDCE' was not declared in this scope
WDTCSR |= (1 << WDCE) | (1 << WDE);
^~~~
C:\Users\cdrum\Documents\Arduino\libraries\MySensors/hal/architecture/AVR/MyHwAVR.cpp:336:18: note: suggested alternative: 'WDIE'
WDTCSR |= (1 << WDCE) | (1 << WDE);
^~~~
WDIE
exit status 1
Error compiling for board ATtiny441/841 (No bootloader).

Thank You!