Script force all 'installDebug' task wait 10 seconds for device attaching.

wait-online-device.gradle

static isAnyDeviceOnline() {
  def start = System.currentTimeMillis()
  def firstTime = true

  while (System.currentTimeMillis() - start < 10000) {
    def out = new StringBuilder()
    def process = 'adb devices -l'.execute()
    process.consumeProcessOutput(out, null)
    process.waitForOrKill(1000)

    if (out.toString().contains("device ")) return

    if (firstTime) {
      firstTime = false
      println 'INFO: Waiting 10s for any ADB device'
      println "${out.toString()}"
    }

    Thread.sleep(1000)
  }

  throw new GradleException('Timeout. Cannot detect any connected online device')
}

gradle.projectsEvaluated {
  // Grab all build types and product flavors
  def buildTypes = android.buildTypes.collect { type -> type.name }
  def productFlavors = android.productFlavors.collect { flavor -> flavor.name }

  // When no product flavors defined, use empty
  if (!productFlavors) productFlavors.add("")

  productFlavors.each { flavor ->
    buildTypes.each { buildt ->
      def task = project.tasks.findByName("install${flavor.capitalize()}${buildt.capitalize()}")
      if (null != task) task.doFirst { isAnyDeviceOnline() }
    }
  }
}

Usage: just copy and paste code into end of the app/build.gradle file