does the MDBT42Q,2v04 have i2c interface?

Then you can write your own module for it, eg: http://www.espruino.com/Writing+Modules

All the source code for other modules is available from their respective pages so it's pretty easy to see what is done and work from there.

As it happens, I have some beta MAX30102 code that hasn't been added as a module yet:

var hrm = (function() { // MAX30102
  var R = {
    INTR_STATUS_1 : 0x00,
    INTR_STATUS_2 : 0x01,
    INTR_ENABLE_1 : 0x02,
    INTR_ENABLE_2 : 0x03,
    FIFO_WR_PTR : 0x04,
    OVF_COUNTER : 0x05,
    FIFO_RD_PTR : 0x06,
    FIFO_DATA : 0x07,
    FIFO_CONFIG : 0x08,
    MODE_CONFIG : 0x09,
    SPO2_CONFIG : 0x0A,
    LED1_PA : 0x0C,
    LED2_PA : 0x0D,
    PILOT_PA : 0x10,
    MULTI_LED_CTRL1 : 0x11,
    MULTI_LED_CTRL2 : 0x12,
    TEMP_INTR : 0x1F,
    TEMP_FRAC : 0x20,
    TEMP_CONFIG : 0x21,
    PROX_INT_THRESH : 0x30,
    REV_ID : 0xFE,
    PART_ID : 0xFF
  };

  var i = new I2C();
  i.setup({scl:P.HRM_SCL,sda:P.HRM_SDA});
  function r(a,n) {
    i.writeTo(87,a);
    return i.readFrom(87,n);
  }
  function w(a,d) {
    i.writeTo(87,[a,d]);
  }

  function init() {
    if (r(R.PART_ID,1)!=0x15) throw new Error("WHO_AM_I failed");
    w(R.MODE_CONFIG,0x40); // reset all
    w(R.INTR_ENABLE_1,0xc0); // INTR setting
    w(R.INTR_ENABLE_2,0x00);
    w(R.FIFO_WR_PTR,0x00);  //FIFO_WR_PTR[4:0]
    w(R.OVF_COUNTER,0x00);  //OVF_COUNTER[4:0]
    w(R.FIFO_RD_PTR,0x00);  //FIFO_RD_PTR[4:0]
    w(R.FIFO_CONFIG,0b10001111);  //sample avg = 4, fifo rollover=false, fifo almost full = 17
    w(R.MODE_CONFIG,0x02);   //0x02 for Red only, 0x03 for SpO2 mode 0x07 multimode LED
    w(R.SPO2_CONFIG,0b00101111);  // SPO2_ADC range = 4096nA, SPO2 sample rate (400 Hz), LED pulseWidth (411uS)
    w(R.LED1_PA,0x3f);   //Choose value for ~ 7mA for LED1
    w(R.LED2_PA,0x3f);   // Choose value for ~ 7mA for LED2
    w(R.PILOT_PA,0x3f);   // Choose value for ~ 8mA for Pilot LED (?)(
  }
  function kill() {
    w(R.MODE_CONFIG,0x40);
  }

  function read() {
    var d = r(R.FIFO_DATA,6);
    return {
      red : (d[0]<<16)|(d[1]<<8)|d[2],
      ir : (d[3]<<16)|(d[4]<<8)|d[5]
    };
  }
  
  function readFifoRaw() {
    var fifo = r(R.FIFO_WR_PTR,3); // wr,overflow,rd
    var s = fifo[0]-fifo[2];
    if (s<=0) s+=32;
    if (fifo[1]) s=32; //overflowed
    var result = [];
    return r(R.FIFO_DATA,3*s);
  }
  
  function decodeRawData(d, red) {
    var l = d.length;
    for (var i=0,n=0;i<l;i+=3,n++) {
      red[n] = (d[i+0]<<16)|(d[i+1]<<8)|d[i+2];
    }
  }

  var h = {
    r:r,w:w,
    init:init,
    kill:kill,
    read:read, // read one
    readFifoRaw:readFifoRaw, // read entire fifo as raw data (32 elements max, 6 bytes each)
    decodeRawData:decodeRawData // decode data read with readFifoRaw
  };
  // IRQ seems not to work at the moment
  //pinMode(P.HRM_INT,"input_pullup");
  //setWatch(function() {
  //  h.emit('data',read());
  //}, P.HRM_INT, {repeat:true,edge:-1});
  // could use with hrm.on('data',x=>print("hrm",x));
  return h;
})();

function getHRM() {
  print("Starting HRM...");
  hrm.init();
  var cnt = 100;
  var rawdata = new Uint8Array(cnt*3);
  var dcnt = 0;
  print("Waiting for HRM... wait 1 second");
  var i = setInterval(function() {
    hrm.readFifoRaw();
  });
  setTimeout(function() {
    print("Reading HRM... wait 10 seconds");
    clearInterval(i);
    hrm.readFifoRaw();
    var t = getTime();
    var i = setInterval(function() {
      d = hrm.readFifoRaw();
      rawdata.set(d, dcnt*3);
      dcnt += d.length/3;
      if (dcnt>=cnt) {
        drawHRM(rawdata);
        dcnt=0;
      }
    }, 1000);
  }, 1000);
}

function drawHRM(rawdata) {
  var cnt = rawdata.length/3;
  var dred = new Uint32Array(cnt);
  hrm.decodeRawData(rawdata, dred);
  var g = Graphics.createArrayBuffer(cnt,60,1);
  var red = E.sum(dred)/cnt;
  g.clear();
  g.drawString("Red",2,2);
  g.moveTo(-100,0);
  for (var i=0;i<cnt;i++) 
    g.lineTo(i,30+(dred[i]-red)/10);
  g.dump();
}

If you want to find out about temperature sensors that are supported out of the box with Espruino, just type 'temperature' into the search box: http://www.espruino.com/Search?kw=temperature