DS18B20 are small true temperature sensors. You can find them easily on ebay for a couple of $.
By default the bugOne use PD5 for this sensors. You can tweak this in devices/onewire.h
#define OW_PIN PD5 #define OW_IN PIND #define OW_OUT PORTD #define OW_DDR DDRD
The default setting for power supply is parasite. Just power the device through a 4.7k pull-up on pin DQ. You can change this in devices/ds18x20.c
int8_t ds18x20_read(struct packet_t *packet) {
uint16_t temperature;
uart_putstr_P(PSTR("ds18x20 read\r\n"));
DS18X20_start_meas(DS18X20_POWER_PARASITE,NULL);
_delay_ms(DS18B20_TCONV_12BIT);
DS18X20_read_decicelsius_single(DS18B20_FAMILY_CODE, &temperature);
return set_data_int16(packet, temperature);
}