Which of the following should be considered when selecting an accessory SWR meter?
Why An SWR meter contains a directional coupler whose sampling circuit is designed for a particular frequency range, so an HF bridge will give bad readings at VHF/UHF and vice versa. It also has a power rating and a meter scale calibrated for a certain range, so a QRP-scale meter can be damaged or pegged by a 100 watt transmitter, and a kilowatt meter barely twitches on 5 watts. Choosing a meter rated for both your band and your output power is what gives accurate, safe readings.
Watch out Distance from the antenna is not a selection criterion, though where you insert the meter does affect what you read; and no SWR meter can compensate for or correct a mismatch, it only measures forward and reflected power.
Pick an SWR meter by frequency and watts, the same two things you'd check on any RF component.