ChickenPing is available to try, unrestricted, for 30 days. By buying a license for £5, you get free updates to minor versions (eg: v2.3 to v2.4, v2.5 etc), and reduced "upgrade" prices for major versions (eg: v2.4 to v3.0).
Still need convincing? ChickenPing gives you all of this:
Image is for illustration only, no physical media is delivered as keys to activate ChickenPing are sent electronically.